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Does bird predation enhance the impact of green muscle[R] (Metarhizium acridum) used for grasshopper control?

Introduction

Locust and grasshopper control in the Sahel still heavily relies on chemical insecticides. During the 2003-05 Desert Locust, Schistocerca gregaria, upsurge in western and northern Africa, over 13 million liters of organophosphate and pyrethroid compounds were used, but no biopesticides (Brader et al. 2006). This is surprising because the entomopathogenic fungus Metarhizium acridum, formerly M. anisopliae var. acridum (Bischoff et al. 2009) (Green Muscle[R], further GM) has been commercially available for operational use since 1999 (Lomer 1999) and has been assessed for use against Desert Locust at a dose rate of 50 g conidia (spores)/ha (PRG 2004). Its use in locust control has meanwhile been recommended by the FAO (Magor 2007, FAO 2009) and it obtained full registration from the "Comite Sahelien des Pesticides" (CSP-CILSS) in nine Sahelian countries in January 2010.

Despite the recommendations and registration, there is still very little operational use of GM in Africa because users a) consider the time lag before the onset of mortality as a constraint, b) find its price prohibitive at the recommended dose rate, c) consider the temperature dependency as a drawback and d) consider current oil-based formulations (OF) as too rapidly deteriorating under prevalent field conditions (e.g., van der Valk 2007).

Meanwhile, it has been shown that the dose rate of GM in grasshopper control can be reduced to 25 g conidia/ha (Mullie & Gueye 2009) without compromising efficacy, making it directly competitive with chemical insecticides. Following these results, the Senegalese Crop Protection Directorate used GM successfully in 2009 in ca 50% of its treatments against the Senegalese Grasshopper Oedaleus senegalensis at a dose rate of 25 g/ha (Khalifa Ndour, DPV Dakar, pers. comm.). New formulations with longer shelf-lives have also been tested and found to perform very well against Desert Locust under operational conditions (Ould Mohamed 2009).

Natural predation of locusts and grasshoppers by vertebrates can be so important that (chemical) control by man becomes redundant (Mullie 2009). Nevertheless, predation is rarely if ever considered in the decision-making processes applied to locust and grasshopper control.

The effect of entomopathogens on the predator-prey relationship is completely different from that of chemical insecticides. In a study design very much comparable with ours described hereafter, but by using the organophosphorous compounds fenitrothion and chlorpyrifos at two different dose rates, Mullie & Keith (1993a) found that apart from direct mortality of 2-7% of the avian community due to anticholinesterase poisoning, bird numbers on transects decreased significantly by as much as 50% following treatments and colonies of Buffalo Weavers, Bubalornis albirostris, were deserted. This was caused by the impact of the organophosphates on nontarget arthropods such that insectivores faced an immediate depletion of their food resources (Mullie & Keith 1991, 1993a, 1993b).

Biopesticides do not kill immediately, as the pathogens need time to develop after insects become infected (Langewald et al. 1999). Because mycopesticides are very selective, no impact on nontarget species occurs (Lomer 1999, Peveling et al. 1999, Mullie & Gueye 2009) and birds neither leave sprayed areas, nor do they become intoxicated. Instead, there are indications that their numbers may temporarily increase (Mullie 2007). The insects become sluggish, and an easy prey for birds, when basking to induce behavioral fever, i.e., by altered thermoregulatory behavior raising body temperature in reaction to infection by a pathogen (Blanford et al. 1998). There is indeed field evidence of synergy between the impact of entomopathogens and predation (Cheke et al. 2006a, 2006b; Mullie 2007), but this has never been tested experimentally.

The current article addresses the question of whether birds do indeed enhance the impact of M. acridum and if so, to what extent and under which conditions. Medium sized plots (400 ha) were sprayed with GM in a field trial and grasshopper and bird densities monitored over an 8-mo period posttreatment. Grasshopper consumption by birds over time was calculated for each of the treatments, based on energetic requirements and compared to available grasshopper biomass. Grasshopper removal rates were assessed to compare treatments.

Methods

Study area.--The study took place from September 2008 until June 2009 at Khelcom, also known under the name of Mbegue, central Senegal (lat 14[degrees]28' - 14[degrees]43' N, long 15[degrees]22' - 15[degrees]36'W).

Between 1991 and 2004, 55,400 ha (as measured by GPS) out of the 73,000 ha Mbegue Sylvo-pastoral Reserve was gradually deforested to allow for groundnut production. However, in 2008 the total cultivated area was only 12.5%, of which about 60% consisted of groundnut and the rest of millet and some smaller surface areas that were grown with crops such as maize, tapioca and sesame. Typically, a field cultivated with groundnut would be sown with millet during the following rainy season one year later, and thereafter left fallow for one or more years. As a consequence, Khelcom is now a mosaic of cropland, fallow and never-cultivated but deforested land, in various stages of succession, mainly with the shrub Guiera senegalensis ('Nger' in Wolof) and regrowth of Combretumglutinosum ('Rat').

Of special mention is the liana Leptadenia hastata (Thiakhat'). This evergreen plant, forming large green patches in an otherwise barren environment, harbors reproducing Pyrgomorphidae throughout the dry season, and is also exploited by other grasshopper species, most notably Cryptocatantops haemorrhoidalis, Metaxymecus gracilipes, Diabolocatantops axillaris and Heteracris annulosa. Hence stands of L. hastata are often favored by acridivorous birds during the dry season.

Except for 15 so-called Daras (small settlements each housing up to several hundred children who receive religious training and labor in the surrounding fields), there are no other permanent dwellings in the area. There are, however, dozens of temporary camps inhabited by seminomadic herders.

Wildfires occur annually at Khelcom between November and the end of the dry season. In Fig. 1, a map of Khelcom is given showing the layout of our experimental plots and of the areas being burnt.

Floristic composition.--The floristic composition of the study plots was assessed from the diagonals which also served as transects for counts of grasshoppers and birds (Fig. 1). In the middle of each subtransect of 100 m the herbs present on a 10x10-m quadrat were identified with Berhaut (1967), Terry (1993) and Sankara (2008), and their coverage (%), height (cm) and the percentage of bare soil noted. Trees and shrubs present were identified with von Maydell (1990) and counted on a 100 x 100-m bloc and their height and number noted.

Meteorology.--Data on rainfall, wind, temperature and relative humidity were obtained from the National Meteorological Station at Touba Khelcom (lat 14[degrees]34'N, long 15[degrees]30'W; Mr Moussa Sy, National Meteorological Service, Khelcom, pers. comm.) situated in the middle of our study area, Fig. 1. Ambient temperatures (T, [degrees]C) and relative humidity (RH, %) values were also recorded with Hobo[R] Pro Series (Onset Computer Corporation, USA, 1998) weather recorders, placed on the ground in the center of each of our plots. The latter observations were believed to provide the best meteorological information of the grasshopper environment and thus for the action of the entomopathogen.

Plots and treatments.--Nine plots of 2 by 2 km, 400 ha per plot, in three blocks of three plots each were delimited. Each block, coded P, Q and R, received three replicate treatments of 0 g (control; P3, Q3, R1), 25 g (P1, Q1, R3) and 50 g (P2, Q2, R2) conidia of M. acridum (strain IMI 330189) per hectare. Plots were at least one kilometer apart to avoid contamination during treatments (Fig. 1).

GM was available in two OF formulations, respectively with 2.5 and 1.25 x [10.sup.13] conidia/l and was mixed in a 1:10 ratio with diesel fuel prior to treatment. Samples of the formulations before mixing were analyzed for viability and concentration of conidia. After calibration plots were treated with four Micronair[TM] AU 8115 rotary atomizers (Micron Sprayers Ltd, UK) mounted on four fourwheel drive pick-up vehicles, operating simultaneously at a speed of 10 km/h, with a track spacing of 50 m, dose rate of 1 l/ha and a flow rate of 833 ml/min. Treatments took place between 9 and 11 October 2008 from 8 till 11 AM and again from 4 till 7 PM. To prevent clogging of the spray system by conidia, filters and hoses of all Micronairs were cleaned repeatedly after several passes.

Deposition of droplets was measured in the center of each of the spray plots by placing oil-sensitive papers over a length of 600 m perpendicular to the spray paths and facing the wind at 15-m intervals, 60 cm above ground level.

Grasshopper availability.--Two monitoring periods were distinguished. A period of intensive monitoring was applied from 4 d before until 18 d after treatment, at three-day intervals, during the month of October 2008. Extensive monitoring (once a month) was applied from November 2008 until May 2009, with the exception of April, when no observations were made. In September, three more series of counts, respectively at 20, 18 and 14 d pretreatment, were made in nine other plots in the same study area, which were to be sprayed aerially. We will also refer to some of the data obtained from these plots.

All observations were done on transects. One of the 2800-m long diagonals of each plot, usually SE-NW, in a few cases NE-SW (Fig. 1), was divided in three transects of 700 m, starting at 250 m from the corner of the plot, with a 100-m buffer between successive transects and again 250 m at the end of the third transect. Each transect was divided in seven subtransects of 100 m to facilitate observations and to differentiate observations spatially. Observations on subsequent transects within the same plot were considered as being independent.

Density.--During the intensive monitoring period, two observers walked on either side of the transects, starting at about one to two hours after sunrise. On each subtransect of 100 m, and spaced at 20-m intervals, five open quadrats of 1 [m.sup.2] were selected at random and total number of grasshoppers (nymphs plus imagos) counted. For each subtransect of 700 m this produced 35 observations or 105 observations for each plot. The densities for the two observers were averaged for each paired quadrat and these figures used in calculations.

[FIGURE 1 OMITTED]

During the extensive monitoring, counts were done by a single observer. As it was anticipated that grasshopper densities and proportion of nymphs would drop during the dry season, making the use of quadrat counts inappropriate, during the last count of the intensive monitoring period, both quadrat and full-transect counts (Cressman 2001) were executed successively on the same transects. All grasshoppers seen within 50 cm on either side of the walked track were counted and totals for each subtransect of 100 m were noted. Average numbers per m2 (x) were subsequently regressed against average numbers counted by the quadrat method (y) on the same subtransect. To make counts during both periods comparable, the regression equation (y = 1.0905x; [r.sup.2] = 0.9388) was used to convert densities counted by transect counts into densities calculated by the quadrat method during the period of intensive monitoring.

Community structure.--As the transect counts did not produce information on individual species, after each count insects were captured with sweep nets. Over the entire diagonal, between the 250-m limits from each corner, on three repetitions each of 150 m, grasshoppers were captured in a way as representative as possible: to assure representation of the various habitats available on the plot and to assure the capture of "difficult" stages, such as first instars (less mobile, difficult to capture when on the ground) and such as adults of the larger grasshoppers, the latter particularly difficult when temperatures were elevated and imagos were highly mobile. To reduce variability among samples and dates and to standardize sampling, the capture continued until at least 500 individuals per plot were trapped during each sampling. To prevent interaction with counts, grasshoppers were captured on an imaginary line which was ca 100 m away from and parallel to the transects.

Grasshopper imagos were identified with Lecoq (1979, 1988, 2008) Mestre (1988) Launois & Launois-Luong (1989) and Launois-Luong & Lecoq (1989). If necessary they were compared to specimens in the reference collection of the Crop Protection Directorate. Nymphs were identified with Popov (1989).

Biomass.--A subsample of the grasshoppers captured for establishing community structure, to which were added individuals captured between September and December 2009 during a follow-up study on the same plots, was used to take both fresh and dry body masses to calculate grasshopper biomass.

Bird numbers.--The same transects and subtransects used for grasshopper counts (see under grasshopper availability) were used for bird counts. As birds were most active in the first hours of daylight and grasshoppers only after they had increased their body temperatures, the onset of bird counts on transects preceded those of grasshoppers, usually starting within the first hour after sunrise. The only exception was when heavy rains prevented an early start. We believe this did not influence the quality and comparability of the counts, as all three observers had the same delays and birds usually exhibited a peak of activity immediately following rains.

As the observers had only basic experience in field ornithology and in estimating distances, the senior author organized a three-day intensive practical training course in the field prior to the onset of the study. Individual performances, both on visual identification and by sound, were tested at the end of the training to assure that the most important and/or most common species could be properly identified. In the course of the monitoring period these training sessions were repeated several times to account for species having newly arrived, e.g., Palaearctic-African migrants. For visual identification of birds Brown et al. (1982), Urban et al. (1986, 1997), Fry et al. (1988, 2000), Keith et al. (1992) and Borrow & Demey (2001) were used. For identification of bird song the CD collections of Chappuis (2000) and Barlow et al. (2002) were used.

To standardize counts temporally (monitoring per plot) and spatially (comparison with other plots), each subtransect of 100 m was counted in 5 min.(cf. Mullie & Keith 1993a), or 35 min per transect. All birds that could be seen with the naked eye or heard at unlimited distance on either side of the transect, were noted on field forms. Binoculars (8x40, 10x40) were used to identify species that otherwise were too distant to be properly identified, or to distinguish between similar species. It was decided not to apply a maximum observation distance a priori, because otherwise the sample of raptors and storks might become too small. However, during analysis (see under statistics) observation width was sometimes limited a posteriori.

For each observation, i.e., a single bird or a group of two or more individuals close together, the number and the distance perpendicular to the transect was noted, according to the methodology of distance sampling (Buckland et al. 1993). Nonidentified species were noted with a description. In many cases these species could later be identified. The Distance software (Thomas et al. 2006) allows for a calculation of true densities, as it accounts for the probability of detection: small or secretive species will only be observed at rather short distances, whereas flocks, large species or species with a conspicuous behavior tend to be noticed at larger distances.

Grasshopper consumption by birds.--Based on existing knowledge of the food and feeding behavior of the bird species present on our transects (cf. Morel & Morel 1978, Mullie & Keith 1993a, Mullie 2009), as well as on the basis of visual observations during the study, on gizzard contents of birds found dead, e.g., as road victims in our study area, and on the contents of regurgitated pellets (see also next paragraph) collected in roosts of communal species such as White Stork, Montagu's Harrier and Lesser Kestrel, Falco naumanni, observed species were classified as acridivorous or nonacridivorous.

As the total observation period, from September till June, included both a part of the rainy season and the major part of the dry season, some species were present in only a part of this period. Certain species such as the Village Weaver, nested and fed their young with insect prey. During the dry season they became granivorous. The Village Weaver is considered as one of the principal predators in Senegal of the Senegalese grasshopper Oedaleus senegalensis during the rainy season (Axelsen et al. 2009). Other common species, such as the Singing Bushlark, Mirafra cantillans, and the White-billed Buffalo Weaver, are acridivorous during the rainy season, feeding themselves and theiryoung with grasshoppers (Mullie & Keith 1993), but become granivorous during the dry season (pers. obs. WCM). Other species may change the proportion of grasshopper prey in their diet throughout the season. As yet, we do not have sufficient information to estimate accurately for each species which proportion of its diet consists of grasshoppers throughout the year.

To be on the conservative side, we assume here that the diet of any species considered to be acridivorous does not consist by more than 50 % of grasshopper prey, even if we know for certain species (Montagu's Harrier, Lesser Kestrel; Mullie 2009) or suspect for others (White Stork, Abyssinian Roller, Coracias abyssinica, Woodchat Shrike, Lanius senator) (this study) that the proportion by weight of grasshoppers in their diet may be as high as 80-90%. Furthermore we follow Axelsen et al. (2009) that any breeding granivorous species only feeds on grasshoppers during the rainy season and from November onwards only feeds on grains.

Individual field metabolic rates (FMRs) of birds were calculated by using an allometric analysis of log-log transformed data of fresh body mass (Mb) in g and FMR in kJ/day of 229 vertebrate species (p<0.007, [F.sub.1227] = 547; [FMR=2.25Mb.sup.0808]) (Nagy2005). A database was developed in Excel (Microsoft Inc.) containing for each record, along with bird species name, number observed and distance, information on bird body mass, FMR, FMR corrected for food digestibility, effective strip width (ESW; see under statistics), origin (Palaearctic or Afro-tropical) and detection probability (Table 1). From these data, bird densities/krm and their grasshopper consumption were calculated.

To estimate the percentage of grasshopper biomass taken daily by the acridivorous bird community, the calculated daily consumption (kg DM/[km.sup.2]) was divided by the calculated daily total biomass of grasshoppers present + daily consumption (kg DM/[km.sup.2]) and multiplied by 100.

Food remains in regurgitated pellets.--Only data on pellet contents from Montagu's Harriers became available during the study; data from other species will be published elsewhere. All Montagu's Harriers feeding in Khelcom used up to 4 communal roosts within the area. During the extensive monitoring period regurgitated pellets were randomly collected in the roosts (ca 100 pellets per roost and per visit), individually wrapped in plastic foil and labelled for future analysis and identification of the prey remains. As the main orthopteran remains in pellets are mandibles, a key had to be developed to identify individual species (Franck Noel, in prep.), taking into account the wear of the mandibles (cf. Chapman 1964, Zouhourian-Saghiri et al. 1983, Gangwere & Spiller 1995, Smith & Capinera 2005). Prey remains per pellet were counted (using maxima of left or right mandibles, tibiae, femurs, and other identifiable parts) and biomass of grasshoppers calculated from data in Appendix 1.

Statistics: grasshopper densities.--Count data were log transformed before analysis. Because data were not independent in time, a BACI (Before-After-Control-Impact) design was applied (Stewart-Oaten et al. 1986). In this design, the effect parameter [Log [(n+1).sub.treated]--Log [[(n+1).sub.control]].sub.before] was tested against [Log[(n+1).sub.treated]--Log[[(n+1).sub.control]].sub.after]. It was thus implicitly assumed that the log difference of 'to be treated' and control plots was constant in time before treatments and that any change in this ratio, after spraying of GM, was caused by a treatment effect.

Statistics: bird densities.--The results from the transect counts were analyzed with the software Distance 5.0, release 2 (Thomas et al. 2006). For each individual species (for common species) or group of species (for less common species) Effective Strip Width (ESW) was calculated, a measure that depends on the probability of detecting a bird. To obtain a larger sample size, the less-common species were grouped into three categories: from 1 (low) to 3 (high) probability of detection. These categories corresponded approximately with detection distances of 0-100 m (1), 0-200 m (2) and 0->400 m (3). For about half the number of bird species, a Hazard Rate model was used to calculate ESW, for the others a Half-normal with Cosine Expansion model. The chosen observation interval was manual in half of the cases and automatic in the others, whereas truncation of observation distance was applied in most cases to allow for a better fit of the chosen model. Details are given in Table 1.

To transform count data into densities, the following formula was applied: Density (ind./[km.sup.2]) = number counted / (2 x 2.1 x ESW). In this formula the factor 2 corrects for the two sides of the transect counted and the factor 2.1 is the total length in km of the three subtransects per plot. As an example we can take 9 Singing Bush-larks counted on a plot, which would give a density of 9/(2 x 2.1 x 0.0326) = 65.73 ind./[km.sup.2] Calculated densities were neither corrected for breeding females nor for nestlings, as was done by Axelsen et al. (2009).

Treatment effects were analyzed by Repeated Measures ANOVA (SPSS, v.13.0; SPPS Inc., Chicago, Illinois, USA). Missing values on day -1 for plots R1 and R2 were obtained by interpolation of count data on days -4 and +3.

[FIGURE 2 OMITTED]

Results

Detailed information on the quality and efficacy of the treatments, droplet deposition, germination and persistence of conidia of M. acridum and of meteorological conditions during treatments is given elsewhere (Mullie & Gueye 2009) and will be summarized here. Germination of spores just prior to the first treatments was 93.6 ([+ or -]1.8) % (n=14) in the 500 g/l formulation and 92.4 ([+ or -]2.5) % (n=17) in the 250 g/l formulation (SenBiotech in litt.). Droplet distribution was regular and similar on all treated plots, with an average of 13 droplets/[cm.sup.2]. Efficacy of treatments, corrected according to Henderson-Til ton (1955) for grasshopper counts on control plots, was 83.8-87.1%. Median Lethal Times (MLT) were 8.24 (95% CL 5.97-10.07) and 8.19 (95% CL 6.58-9.74) days and [LT.sub.80] values were15.85 (95% CL 11.99-28.00) and 13.06 (95% CL 10.93-17.11) days respectively for 25 and 50 g/ha, with no differences between the two dose rates. The maximum effect of GM was between 6 and 12 d posttreatment. Mortality of >90% due to Metarhizium infection (confirmed by sporulation) of untreated grasshoppers placed in persistence cages on treated plots for 72 h, showed that M. acridum activity persisted for at least 18 d post treatment.

[FIGURE 3 OMITTED]

Meteorological conditions.--Daily and cumulative rainfall during the 2008 rainy season are given in Fig. 2. Minimum and maximum daily temperatures at ground level during October are given in Fig. 3. The 2008 rainy season at Khelcom was characterized by extremely wet conditions and a cumulative rainfall of 935 mm, which is well above normal and approximately twice the annual amount of the past 20 y in the same area. No rains were recorded during treatments and the following period of intensive monitoring. The interval of minimum and maximum daily temperatures during treatments and thereafter was favorable for a rapid development of M. acridum, as the optimum ambient temperature range for the pathogen development is between 24 and 38[degrees]C (C. Kooyman, FAES Dakar, pers. comm.).

Floristic composition.--Average shrub density in our plots was 17.9 shrubs/ha and consisted of G. senegalensis, C. glutinosum, Balanites aegyptica, Calotropis procera, Cassia occidentalis and Bauhinia rufescens. Tree density was 1.3 trees/ha, the commonest tree being C. glutinosum. Locally stands of Baobabs, Adansonia digitata, had been saved to provide shade for man and livestock. More rarely Tamarindus indica, Piliostigma reticulatum, Mitragyna inermis (in temporary flooded depressions), Acacia (Faidherbia) albida or Sterculia setigera were still present. The few remaining trees are heavily exploited for firewood and browse.

The herbaceous layer was mainly composed of Gramineae, such as Andropogon sp., Cenchrus biflorus ('Cram cram'), Ctenium elegans, Eragrostis tremula, E. tenella and Digitaria sp. Adventives such as Mitracarpus villosus and Spermacoce (Borreria) radiata dominated on sites which had been cultivated in recent years.

Wildfires.--In November 6046 ha of Khelcom was burnt, whereas throughout the dry season, but in particular during April-May, an additional 1307 ha fell prey to wildfires, making a total of 13.4 % of Khelcom being burnt during the study. Some of our plots were partially affected by the fires. Based on our monitoring, this concerned 5.3% of the transects in November, 13.2% from December till March and 18.0% in May.

Grasshopper densities.--Immediately prior to treatments, average densities of grasshoppers (all stages confounded) were between 30 and 35 ind./[m.sup.2] in all plots (Fig. 4). At the end of second decade of September (not shown in Fig. 4), three weeks prior to treatments, average densities of 90 ind./[m.sup.2] were even recorded. Densities remained at pretreatment levels in the control plots until 15 d posttreatment, after which date they gradually decreased due to natural factors related to the end of the rainy season.

[FIGURE 4 OMITTED]

Starting from day 6 after treatment, grasshopper densities in both the 25 and 50 g/ha treated plots decreased rapidly as a result of exposure to M. acridum conidia, which was confirmed by sporulation of M. acridum on caged individuals.

Grasshopper numbers remained low in treated plots and were statistically different from densities in control plots until 74 d after treatment. Only from 109 d posttreatment onwards (January), densities on all plots were no longer different from each other (Fig. 4).

Grasshopper community structure.--In total, 79,480 grasshoppers were captured and identified. The grasshopper community consisted of at least 32 species. In addition, 5 taxa could only be identified to the genus level and at least one or more species remained unidentified. The latter category was only 0.3 % of the total number captured. For 31 species and seven stages (adult and 6 larval stages) fresh body mass (WW, n=1731) and dry body mass (DW, n=908) were taken (Appendix 1). For species and stages for which only fresh body masses were available, these were multiplied by 0.3 to obtain DW values (based on Appendix 1; n=908, ratio DW/WW=0.295). For two rarely captured species lacking field information on body mass (Aiolopus simulatrix and Homoxyrrhepes punctipennis), a regression analysis was obtained from body length vs DW of the captured specimens and the regression equation applied to body-length data from the literature (Mestre 1988), to calculate corresponding DW (imagos only).

On the basis of numbers captured, the Senegalese grasshopper Oedaleus senegalensis (producing diapausing eggs at the end of the rainy season) dominated during the rainy season (58-66%), and was absent from February onwards. Species with diapausing adults or continuous reproduction were present during the entire period (Fig. 5). Numerically the most important species were Acorypha clara, Acrotylus blondeli, Ornithacris cavroisi, Pyrgomorpha cognata complex and P. vignaudi. These species, together with O. senegalensis, comprised 75-85 % of grasshopper numbers in the community at any moment.

On the basis of body mass, the situation is slightly different. O. senegalensis dominated during the rainy season (47%), followed by O. cavroisi (14%), Acoryphaglaucopsis (9%) and A. clara (7%). These four species represented 77% of the grasshopper community. During the dry season, from December onwards, O. cavroisi (53%) A. clara (23%) and Diaolocatantops axillaris (6 %), represented 82% of the grasshopper community by biomass. From December onwards Catantopinae (D. axillaris, Harpezocatantops stylifer, Catantops stramineus, Cryptocatantops haemorhoidalis) and Pyrgomorphidae replaced species laying diapausing eggs (O. senegalensis, A. glaucopsis). In Fig. 6, the grasshopper biomass in time in kg DW/[km.sup.2] is given.

[FIGURE 5 OMITTED]

Birds.--During transect counts, 83 bird species were identified. Of these, 42 were classified as acridivorous, at least during a part of the time (Table 1). In Table 1, details are also given on the various parameters used for calculating densities. Tables with detailed count results per plot and per species can be found in Mullie & Gueye (2009) and are summarized in Appendix 2.

The bird community consisted of a mix of Palaearctic-African (all migratory) and afro-tropical (both migratory and resident) species. Consequently, during the course of the study some species arrived, while others left our study area.

[FIGURE 6 OMITTED]

Commensalistic feeding associations were common and contributed to an efficient removal of grasshoppers from plots. Species implicated were White-billed Buffalo Weaver, White-throated Bee-eater Merops albicollis, White Stork, Lesser Kestrel, Cattle Egret Bubulcus ibis (Fig. 7) and Abyssinian Roller.

The results from the repeated measures ANOVA applied to acridivorous bird species on transects, showed a significant time effect (F=8.582, df=4.562 (Huynh-Feldt correction), p<0.001) but independent of treatment (N.S.): bird numbers gradually increased over time on all plots, with no differences between treatments (Mullie & Gueye 2009).

Although bird numbers were not influenced by treatments, absolute grasshopper consumption by birds increased on all plots, whereas daily removal rates increased on treated plots only. From day -4 until day 6, treated and control plots were not different. Starting from day 9 until day 18, daily removal of the available grasshopper biomass on treated plots increased tenfold from 0.04 0.08% to 0.48%, whereas grasshopper consumption on control plots remained at a low 0.03-0.04% daily removal in the same period (Fig. 8).

The increase of grasshopper removal was due to a combination of two factors. Firstly, and most importantly, GM treatments caused a strong reduction of grasshopper densities, while densities of acridivorous birds did not significantly change. Secondly, although acridivorous bird densities remained in the same order of magnitude, the species composition changed due to migration, with generally heavier migrant species such as Montagu's and Marsh Harriers (C. aeruginosas) arriving and smaller species such as White-throated Bee-eaters and Woodland Kingfishers [Halcyon senegalensis) leaving (Appendix 2).

From 18 till 74 d posttreatment, treated and control plots remained significantly different. In this period both removal rates and consumption continue to increase, as more and heavier bird species arrived, White Storks in particular. From January (day 109) onwards, grasshopper removal rates level off at 1.58 ([+ or -]0.25)% daily removal and are no longer different between treatments.

To verify the validity of our approach, we also calculated grasshopper removal from monthly decreases in densities on control plots from December onwards (interval between dashed lines in Fig. 8). Control plots were taken to avoid confounding factors such as a prolonged mortality due to persistence of viable M. acridum conidia. The results are very much in agreement with the calculations based on enegetic requirements, although the grasshopper removal rate is slightly lower at 1.07 ([+ or -]0.63)%.

As the community structure data did not provide any evidence for major grasshopper immigration to or emigration from the plots from December onwards, it was assumed that population declines on plots in this period were mainly resulting from predation. The daily population decline, as calculated by regression analysis on Log n ind./[m.sup.2] (y) in time (x): (y=-0.0882x + 0.7427, [r.sup.2]=0.9304; ANOVA: df=524, F=7.097, p=0.008; Fig. 9) showed that the rate of decrease of grasshopper densities between December and May was constant. In December, average densities had fallen to below 5 ind./[m.sup.2].

The composition of the bird community changed considerably during the course of the study. During the rainy season it consisted of about 90% acridivores, dropping to ca 10% in May (Fig. 10). However, this change was not caused by decreasing densities of acridivorous birds ((ANOVA; df=9, F=1.671, N.S.), but by a very strong increase of granivorous species during the dry season, most notably Golden Sparrows (ANOVA; df=9, F=48.456, p<0.001).

Pellet contents.--Based on numbers of prey items recovered from Montagu's Harrier pellets in the period January to March, grasshoppers constitute 87.4-91.0% of the diet, whereas on the basis of biomass, they constitute 51.0-61.0% (Mullie & Koks unpub. data). In Table 2, recovered grasshopper species are given from high to low body mass. The harriers do not take grasshoppers proportionally to their occurrence ([chi square] (13, n=1623) = 3701.04, p < 0.0001). Common species (i.e., > ca 5% of the community) with a body mass > 0.73g are taken significantly more often than smaller species. The latter represent only 1.4-2.6% of all grasshoppers being taken by the harriers, whereas they represent 61-68% of the grasshopper community in the field. The three preferred prey species in order of importance are Acorypha clara (57-65%), Ornithacris cavroisi (23-26%) and Diabolocatantops axillaris (9-15%).

[FIGURE 7 OMITTED]

Discussion

The 2008 rainy season at Khelcom was characterized by exceptionally abundant rainfall (935 mm) and very high grasshopper densities (up to 90 ind./[m.sup.2] in September, 30-35 in October) showing a low mobility. This low mobility can be explained by the presence of a well-developed herbaceous layer, due to abundant rainfall and by the absence of favorable winds at the right moment for the second generation of the Senegalese Grasshopper to migrate north (J. Bak, National Environmental Research Institute, DMU, Denmark, pers. comm.). This resulted in two subsequent generations of O. senegalensis reproducing at Khelcom, leading to very high densities. The treatments with GM were executed against a population of O. senegalensis of which adults predominantly belonged to the second generation, and nymphs to the third generation.

The composition of the grasshopper community, consisting of 32+ species, was dominated numerically by the Senegalese grasshopper (58-66%) before treatments and during the intensive monitoring period at the end of the rainy season, but in terms of both numbers and biomass, species with diapausing adults such as O. cavroisi and

[FIGURE 8 OMITTED]

A. clara, were common throughout the entire study period (Fig. 5). Their continuous presence is likely the main reason that they form an important part of the diets of many acridivorous birds (Mullie 2009). Nymphs were the dominant life-form until mid-October. Starting from December onwards, only nymphs of continuously reproducing species were present.

In recent years Khelcom has become an important reproduction area for an array of grasshopper species, some of which are important pests to rain-fed agriculture. Until 1991, Khelcom was part of the 73,000-ha protected Mbegue Sylvo-Pastoral Reserve, of which 55,400 ha were gradually cleared until 2004 to make way for groundnut production. Grasshopper problems were unknown from the area before 1991 (data from Crop Protection Directorate). The resulting mosaic of cropped areas (not exceeding 12.5% of the surface area during the study), fallow and cleared land and partially regenerating former forest, has become an ideal habitat for grasshopper development. This in turn has attracted acridivorous bird species, such as Montagu's Harrier, characteristic for areas rather low in the succession cycle. Numbers of Montagu's Harriers that use Khelcom either for foraging or as a night roost are maximally 5000-6000 individuals (Mullie & Gueye 2009). These numbers are unprecedented elsewhere and are among the highest recorded anywhere in the world (Clarke 1996). They constitute about 16% of the population of about 37,000 individuals estimated to migrate via Spain to the African mainland (B. Koks, SWGK, The Netherlands, pers. comm.) and 2% of the entire world population estimated at 300,000 individuals (C. Trierweiler, Groningen University, The Netherlands, in litt.).

[FIGURE 9 OMITTED]

Some of the other acridivorous species reach very high densities, rarely found in such concentrations elsewhere in the Sahel, e.g., White Stork (3,500 ind.; 1.75% ofthe flyway population) and Lesser Kestrel (5,000; 10%) (Mullie & Gueye 2009). All these species exceed the 1% criterion for areas of international ornithological importance (Ramsar Convention-COP9 2005; www.ramsar.org/key_criteria) and are protected under the Bonn Convention of which Senegal is signatory (CMS-COP9 2008).

[FIGURE 10 OMITTED]

The consistent data of the temporal composition of the structure of the community supports the hypothesis that grasshopper movements during the entire study period were rather limited and that continuously decreasing densities between December and May were largely caused by predation. They logarithmically decreased (all species combined) from 4.66 ind./[m.sup.2] in December to 1.51 ind./[m.sup.2] in May, or a reduction of 67.2%. A constant decrease of grasshoppers due to predation started at densities below ca 5 ind./[m.sup.2], which can be considered as a medium density. Total grasshopper biomass was reduced from 1,256 kg DW/[km.sup.2] in December to 352 kg DW/[km.sup.2] in May, a reduction of 71.9%. Some local displacements, might have occurred as dead grasshoppers, in particular Diabolocatantops axillaris, showing sporulation of M. acridum, were found up to 12km from the nearest treated plots in October and November (Mullie & Gueye 2009), and also the small increase of densities on treated plots between December and January may have been the result of either local redistribution of grasshoppers or of small-scale immigration.

An important finding of this study is that GM did not have an impact on bird numbers and densities; these changed significantly over time, but were unrelated to treatments. [Treatments of grasshoppers with the organophosphates (OPs) chlorpyrifos and fenitrothion in Senegal were shown to have large and significant negative effects on bird displacements, apart from direct mortality and reproduction effects (Mullie & Keith 1993).]

While numbers of acridivorous bird species did not change, their biomass did when heavier migrant species arrived. This increased grasshopper removal rates on all plots, but more steeply on treated plots, because grasshopper densities had already been affected by GM. It is only at 3.5 mo posttreatment that grasshopper removal rates level off and are no longer different from controls. Hence by increasing the duration of the GM impact (Fig. 8), bird predation enhanced its action.

When taking body size into account, we observed that large (O. cavroisi) and medium-bodied (A. clara) species significantly declined, whereas small-bodied species (Pyrgomorphidae) first increased adult population levels, to decline only during the last count. Grasshopper remains from Montagu's Harrier pellets show the same tendency: small bodied grasshoppers (< 0.73 g) represented < 2.6% of the prey by body mass, while they represented 61-68% of the grasshopper community in the field. Montagu's Harriers preyed preferentially on A. clara, O. cavroisi and other medium bodied species such as D. axillaris. [Lesser Kestrels also prey preferentially on O. cavroisi (Mullie 2009).]

Our data also confirm earlier findings of Branson (2005b) who reported that birds reduced the proportion of medium-bodied grasshoppers, while small-bodied grasshoppers increased in abundance. Belovsky & Slade (1993) found a predation-mediated reduction of large-bodied grasshoppers, whereas changes in abundance of medium and small-bodied species that they observed could not be explained by predation.

There was a large difference between grasshopper removal during the rainy season and during the dry season. Because most grasshoppers reproduced between September and November, predation by birds could not be calculated in the same way as during the dry season. Therefore, cumulative daily predation rates were integrated over time (September--November) to obtain an estimate of the total predation during this period. As vegetation development started at the onset of the first significant rains (i.e., > ca 20 mm), which was in mid-June (Fig. 2) and grasshopper reproduction soon afterwards, our data do not cover the entire reproductive period and the importance of predation may have been underestimated. Nevertheless, predation did not remove more than 1% from the community, which can be considered as insignificant. This is in contrast with modelling results presented by Axelsen et al. (2009) that birds reduce O. senegalensis populations in Senegal and Niger during the rainy season by 20-25%. It should be mentioned that bird densities in their study have been corrected for breeding females and for nestlings as well as for reduced reproductive output of the grasshopper population, but this alone does not explain the large difference.

Data from North American studies are much more variable. Predation rates of 30-50% have been reported at low and medium grasshopper densities (Joern 1986, 1992; Fowler et al. 1991; Bock et al. 1992). However, in some cases no measurable effect of predation was present (Joern 2000). Our data are corroborated by those of Branson (2005) who states that bird predation becomes less important at high grasshopper densities, which was also the case during the rainy season in our study. However, when grasshopper densities decreased to medium levels (ca 5 ind./[m.sup.2]), bird predation became very important.

The removal of grasshoppers by birds was calculated under some broad assumptions about diet composition (maximum 50% of the diet of acridivorous species supposed to be composed of grasshoppers) and temporal aspects of predation (granivorous species which were known to feed on acridids during their breeding season were supposed not to do so from December onwards). As compared to calculations derived from grasshopper densities in successive months, calculations from bird consumption produced very similar results, supporting the idea that under conditions of less stable grasshopper populations, bird consumption of grasshoppers can be approximated by a few rough assumptions about predation rates, if the densities of acridivorous species have been assessed. The peak in consumption in November and December (days 47-74) in Fig. 8 is due to the presence of large concentrations of White Storks on some of the plots treated with 50 g conidia/ha, which has a strong influence on calculated biomass removal. The shape of the curves of grasshopper removal calculated from monthly biomass reduction (dashed lines in Fig. 8) strongly suggests that White Storks had also been present on control plots, but were not seen during the monthly count.

Commensalism may be an advantageous strategy for feeding on orthopterans in particular, in dense vegetation and at high grasshopper densities. In addition to our observations, Cheke et al. (2006a, b) observed Lanners, Falco biarmicus, exploiting Desert Locust by following men and camels in dense Schouwia thebaica vegetation in Northern Niger and stooping on locusts being flushed. Jensen et al. (2008) very frequently observed Lanners exploiting grasshoppers (probably O. senegalensis) flushed by Abdim's Storks, Ciconiaabdimii, in SE Niger. In Waza National Park (Extreme North of Cameroon), Ralph Buij (in litt.) observed Yellow-billed Kites, Milvus parasitus, doing the same when people flushed grasshoppers in high grass. He also observed Northern Carmine Bee-eaters, Merops nubicus, with goats (they also travel on goatbacks) and Arabian Bustards, Ardeotis arbabs, and Piapiacs, Ptilostomus afer, with small livestock, and Abyssinian Rollers with Abdim's Storks at the start of the rains. Only once two adult Montagu's Harriers were observed flying amongst a herd of over 200 cattle catching flushed grasshoppers (Ralph Buij, in litt.).

Deforestation for expansion of groundnut production destroyed the formerly protected forest at Khelcom, reputedly with a high biodiversity (Schoonmaker-Freudenberger 1991). In turn it also created a habitat low in the succession cycle and rich in orthopterans and their predators. Some of them, such as the Montagu's Harrier, are so abundant that their numbers are unprecedented anywhere else in the world. The semi-arid Sahelian agricultural habitat is currently under a severe human pressure (Zwarts et al. 2009) and avian predators in the Sahel have faced a decline of over 90% in the last 30 years (Thiollay 2006a, b). Biopesticides and predators can play a vital role in controlling grasshoppers considered to be a pest to agriculture without compromising agro-ecosystem functioning. Therefore their complementary role should be exploited instead of neglected.

Acknowledgements

We sincerely thank the more than 30 people who participated in the field work for this study. The study would not have been possible without the financial support of the Japanese Embassy in Dakar, through the KR2 programme. The Dutch Foundation Working Group Montagu's Harrier (SWGK) contributed financially to the pellet analysis. Special thanks are due to the directors of the Agriculture Directorate, Mr Samba Kante and Mamadou Diallo, and director of the Crop Protection Directorate, Mrs Marietou Diawarra for logistic support and for providing human resources. Kemo Badji provided untold assistance during treatments and throughout the intensive monitoring period. We thank Aliou Badji and Kalilou Bodiang who formed part of the team which executed the extensive monitoring, Franck Noel who analyzed the pellets and developed a key for mandible identification and Christiane Trierweiler who gave statistical advice. Helpful comments on earlier drafts of this paper were provided by Drs Michel Lecoq, Bo Svenning Petersen, Christiane Trierweiler, Glenn Morris and three anonymous referees. They are kindly acknowledged.
Appendix 1. Fresh (WW) and dry body mass (DW) of grasshoppers captured
on plots and used for calculations of grasshopper biomass.

                                             imago

Species                            n      WW      n      DW

Atractomorpha acutipennis          2    0.184     -       -
Acrida bicolor                    32    0.912     20    0.307
Acrotylus blondeli                 8    0.072     5     0.041
Acorypha clara                    176   0.889    172    0.386
Acorypha glaucopsis               59    1.518     25    0.270
Acorypha picta                    25    0.568     -       -
Acanthacris ruficornis citrina     -      -       -       -
Acridoderes strenuus               9    1.120     2     0.245
Acrida sulphuripennis              -      -       -       -
Cataloipus cymbiferus              5    4.356     -       -
Cataloipus fuscocoeruleipes        -      -       -       -
Cryptocatantops haemorrhoidalis   50    0.214     32    0.085
Chrotogonus senegalensis          16    0.289     9     0.112
Catantops stramineus               8    0.505     -       -
Diabolocatantops axillaris        54    0.729     10    0.288
Duronia chloronota                 2    0.155     2     0.050
Heteracris annulosa               20    0.773     18    0.352
Hieroglyphus daganensis            3    3.407     1     1.429
Harpezocatantops stylifer          7    0.226     7     0.114
Humbe tenuicornis                  -      -       -       -
Kraussella amabile                46    0.426     7     0.068
Kraussaria angulifera             16    3.073     1     0.638
Morphacris fasciata                1    0.153     1     0.052
Metaxymecus gracilipes             2    0.422     -       -
Ornithacris cavroisi              175   2.661    163    1.177
Oedaleus nigeriensis               5    0.598     5     0.230
Oedaleus senegalensis             153   0.534     25    0.128
Pyrgomorpha cognata complex       26    0.088     26    0.041
Pyrgomorpha vignaudii             12    0.195     2     0.047
Truxalis longicornis               2    1.568     -       -
Truxalis sp.                       1    0.317     1     0.094
Zacompsa festa                     9    0.181     2     0.034

n total WW                        924

n total DW                                       536

                                              L1

Species                            n      WW      n      DW

Atractomorpha acutipennis          -      -       -       -
Acrida bicolor                     1    0.005     1     0.001
Acrotylus blondeli                 -      -       -       -
Acorypha clara                    34    0.022     19    0.008
Acorypha glaucopsis                4    0.036     4     0.011
Acorypha picta                     -      -       -       -
Acanthacris ruficornis citrina     -      -       -       -
Acridoderes strenuus               -      -       -       -
Acrida sulphuripennis              -      -       -       -
Cataloipus cymbiferus              -      -       -       -
Cataloipus fuscocoeruleipes        -      -       -       -
Cryptocatantops haemorrhoidalis    -      -       -       -
Chrotogonus senegalensis           -      -       -       -
Catantops stramineus               -      -       -       -
Diabolocatantops axillaris         -      -       -       -
Duronia chloronota                 -      -       -       -
Heteracris annulosa                -      -       -       -
Hieroglyphus daganensis            -      -       -       -
Harpezocatantops stylifer          -      -       -       -
Humbe tenuicornis                  -      -       -       -
Kraussella amabile                 -      -       -       -
Kraussaria angulifera              -      -       -       -
Morphacris fasciata                -      -       -       -
Metaxymecus gracilipes             -      -       -       -
Ornithacris cavroisi              25    0.029     16    0.010
Oedaleus nigeriensis               -      -       -       -
Oedaleus senegalensis             44    0.018     20    0.006
Pyrgomorpha cognata complex        2    0.007     2     0.002
Pyrgomorpha vignaudii              2    0.006     2     0.002
Truxalis longicornis               -      -       -       -
Truxalis sp.                       -      -       -       -
Zacompsa festa                     -      -       -       -

n total WW                        112

n total DW                                        64

                                              L2

Species                            n      WW      n      DW

Atractomorpha acutipennis          -      -       -       -
Acrida bicolor                     8    0.042     2     0.006
Acrotylus blondeli                 -      -       -       -
Acorypha clara                    65    0.062     31    0.018
Acorypha glaucopsis               11    0.123     8     0.020
Acorypha picta                     -      -       -       -
Acanthacris ruficornis citrina     2    0.707     -       -
Acridoderes strenuus               -      -       -       -
Acrida sulphuripennis              -      -       -       -
Cataloipus cymbiferus              -      -       -       -
Cataloipus fuscocoeruleipes        -      -       -       -
Cryptocatantops haemorrhoidalis    -      -       -       -
Chrotogonus senegalensis           4    0.041     2     0.008
Catantops stramineus               -      -       -       -
Diabolocatantops axillaris         -      -       -       -
Duronia chloronota                 -      -       -       -
Heteracris annulosa                -      -       -       -
Hieroglyphus daganensis            2    0.084     2     0.025
Harpezocatantops stylifer          -      -       -       -
Humbe tenuicornis                  -      -       -       -
Kraussella amabile                 7    0.060     1     0.030
Kraussaria angulifera              2    0.587     -       -
Morphacris fasciata                -      -       -       -
Metaxymecus gracilipes             -      -       -       -
Ornithacris cavroisi              40    0.071     25    0.025
Oedaleus nigeriensis               -      -       -       -
Oedaleus senegalensis             51    0.055     30    0.015
Pyrgomorpha cognata complex        2    0.016     2     0.005
Pyrgomorpha vignaudii              2    0.010     2     0.003
Truxalis longicornis               -      -       -       -
Truxalis sp.                       -      -       -       -
Zacompsa festa                     -      -       -       -

n total WW                        196

n total DW                                       105

                                              L3

Species                             n     WW     n     DW

Atractomorpha acutipennis           -      -     -      -
Acrida bicolor                      2    0.092   2    0.027
Acrotylus blondeli                  -      -     -      -
Acorypha clara                     40    0.193   18   0.038
Acorypha glaucopsis                 9    0.265   5    0.076
Acorypha picta                      -      -     -      -
Acanthacris ruficornis citrina      -      -     -      -
Acridoderes strenuus                -      -     -      -
Acrida sulphuripennis               -      -     -      -
Cataloipus cymbiferus               5    0.078   2    0.045
Cataloipus fuscocoeruleipes         -      -     -      -
Cryptocatantops haemorrhoidalis     -      -     -      -
Chrotogonus senegalensis            7    0.067   4    0.024
Catantops stramineus                -      -     -      -
Diabolocatantops axillaris          -      -     -      -
Duronia chloronota                  2    0.105   2    0.035
Heteracris annulosa                 -      -     -      -
Hieroglyphus daganensis             1    0.108   1    0.030
Harpezocatantops stylifer           -      -     -      -
Humbe tenuicornis                   2    0.123   1    0.050
Kraussella amabile                 27    0.121   9    0.055
Kraussaria angulifera               2    0.938   -      -
Morphacris fasciata                 -      -     -      -
Metaxymecus gracilipes              1    0.334   -      -
Ornithacris cavroisi               47    0.228   26   0.064
Oedaleus nigeriensis                3    0.078   3    0.021
Oedaleus senegalensis              53    0.134   18   0.050
Pyrgomorpha cognata complex         2    0.028   2    0.008
Pyrgomorpha vignaudii               1    0.020   1    0.005
Truxalis longicornis                -      -     -      -
Truxalis sp.                        1    0.071   1    0.024
Zacompsa festa                      2    0.062   2    0.017

n total WW                         207

n total DW                                       97

                                              L4

Species                             n     WW     n     DW

Atractomorpha acutipennis           -      -     -      -
Acrida bicolor                      8    0.343   1    0.038
Acrotylus blondeli                  1    0.034   1    0.010
Acorypha clara                     32    0.383   7    0.072
Acorypha glaucopsis                15    0.722   4    0.170
Acorypha picta                      -      -     -      -
Acanthacris ruficornis citrina      8    1.509   -      -
Acridoderes strenuus                -      -     -      -
Acrida sulphuripennis               -      -     -      -
Cataloipus cymbiferus               1    0.046   -      -
Cataloipus fuscocoeruleipes         2    0.473   2    0.158
Cryptocatantops haemorrhoidalis     -      -     -      -
Chrotogonus senegalensis            9    0.127   7    0.037
Catantops stramineus                -      -     -      -
Diabolocatantops axillaris          -      -     -      -
Duronia chloronota                  2    0.159   2    0.048
Heteracris annulosa                 -      -     -      -
Hieroglyphus daganensis             7    1.316   -      -
Harpezocatantops stylifer           -      -     -      -
Humbe tenuicornis                   1    0.120   1    0.040
Kraussella amabile                 14    0.148   5    0.079
Kraussaria angulifera               4    1.430   -      -
Morphacris fasciata                 -      -     -      -
Metaxymecus gracilipes             11    0.490   -      -
Ornithacris cavroisi               35    0.501   16   0.136
Oedaleus nigeriensis                -      -     -      -
Oedaleus senegalensis              39    0.223   10   0.086
Pyrgomorpha cognata complex         2    0.040   2    0.010
Pyrgomorpha vignaudii               -      -     -      -
Truxalis longicornis                1    1.188   -      -
Truxalis sp.                                     -      -
Zacompsa festa                      -      -     -      -

n total WW                         192

n total DW                                       58

                                              L5

Species                             n     WW     n     DW

Atractomorpha acutipennis           -      -     -      -
Acrida bicolor                      5    0.808   2    0.283
Acrotylus blondeli                  -      -     -      -
Acorypha clara                     15    0.638   3    0.181
Acorypha glaucopsis                 6    1.064   6    0.339
Acorypha picta                      -      -     -      -
Acanthacris ruficornis citrina      1    1.161   -      -
Acridoderes strenuus                -      -     -      -
Acrida sulphuripennis               1    0.631   1    0.170
Cataloipus cymbiferus               1    0.505   1    0.148
Cataloipus fuscocoeruleipes         1    0.236   1    0.068
Cryptocatantops haemorrhoidalis     -      -     -      -
Chrotogonus senegalensis            6    0.099   6    0.035
Catantops stramineus                -      -     -      -
Diabolocatantops axillaris          -      -     -      -
Duronia chloronota                  1    0.205   1    0.063
Heteracris annulosa                 -      -     -      -
Hieroglyphus daganensis             -      -     -      -
Harpezocatantops stylifer           -      -     -      -
Humbe tenuicornis                   -      -     -      -
Kraussella amabile                  3    0.315   3    0.100
Kraussaria angulifera               2    1.711   -      -
Morphacris fasciata                 1    0.207   1    0.069
Metaxymecus gracilipes              2    0.478   -      -
Ornithacris cavroisi               23    1.304   12   0.237
Oedaleus nigeriensis                -      -     -      -
Oedaleus senegalensis              21    0.389   6    0.141
Pyrgomorpha cognata complex         1    0.044   1    0.010
Pyrgomorpha vignaudii               -      -     -      -
Truxalis longicornis                -      -     -      -
Truxalis sp.                        -      -     -      -
Zacompsa festa                      -      -     -      -

n total WW                         90

n total DW                                       44

                                              L6
                                                              n WW
Species                             n     WW     n     DW     Total

Atractomorpha acutipennis           -      -     -      -       2
Acrida bicolor                      -      -     -      -      56
Acrotylus blondeli                  -      -     -      -       9
Acorypha clara                      -      -     -      -      362
Acorypha glaucopsis                 -      -     -      -      104
Acorypha picta                      -      -     -      -      25
Acanthacris ruficornis citrina      -      -     -      -      11
Acridoderes strenuus                -      -     -      -       9
Acrida sulphuripennis               -      -     -      -       1
Cataloipus cymbiferus               -      -     -      -      12
Cataloipus fuscocoeruleipes         -      -     -      -       3
Cryptocatantops haemorrhoidalis     -      -     -      -      50
Chrotogonus senegalensis            -      -     -      -      42
Catantops stramineus                -      -     -      -       8
Diabolocatantops axillaris          -      -     -      -      54
Duronia chloronota                  -      -     -      -       7
Heteracris annulosa                 -      -     -      -      20
Hieroglyphus daganensis             -      -     -      -      13
Harpezocatantops stylifer           -      -     -      -       7
Humbe tenuicornis                   -      -     -      -       3
Kraussella amabile                  -      -     -      -      97
Kraussaria angulifera               -      -     -      -      26
Morphacris fasciata                 -      -     -      -       2
Metaxymecus gracilipes              -      -     -      -      16
Ornithacris cavroisi               10    1.487   4    0.314    355
Oedaleus nigeriensis                -      -     -      -       8
Oedaleus senegalensis               -      -     -      -      361
Pyrgomorpha cognata complex         -      -     -      -      35
Pyrgomorpha vignaudii               -      -     -      -      17
Truxalis longicornis                -      -     -      -       3
Truxalis sp.                        -      -     -      -       2
Zacompsa festa                      -      -     -      -      11

n total WW                         10                         1731

n total DW                                       4             908

Appendix 2. Number of birds observed per species and per count from 18
d before until 233 d after treatment. Acridivorous and nonacridivorous
species are given separately.

                             Number of days after treatment

Scientific Name              -18    -14    -4     -1     3

nonacridivorous

Anthus sp.                    -      -      -     -      -
Apus affinis                  -      -      -     -      -
Apus apus                     1      -     15     1      -
Aquila rapax                  -      -      -     -      -
Ardea cinerea                 -      4      -     -      -
Asio flammeus                 -      -      -     -      -
Bubalornis albirostris        -      -      -     -      -
Buphagus africanus            -      -      -     -      -
Calandrella brachydactyla     -      -      -     -      -
Camaroptera brachyura         -      1      -     1      -
Cercotrichas podobe           -      -      -     -      -
Ciconia nigra                 -      -      -     -      -
Cinnyris pulchellus           1      1      -     -      -
Circaetus beaudouini          -      1      -     -      -
Circaetus cinereus            -      -      -     -      -
Circaetus gallicus            -      -      -     -      -
Corvus albus                  -      -      -     -      -
Crinifer piscator             -      -      -     -      -
Delichon urbica               -      -      -     -      7
Eremopterix leucotis          -      -      -     -      -
Eremopterix nigriceps         -      -      -     -      -
Euodice cantans               -      -      -     -      -
Euplectes franciscanus        -      -      9     -      1
Falco ardosiaceus             -      -      -     -      3
Falco chicquera               2      -      3     -      -
Falco sp.                     -      -      -     -      -
Ficedula hypoleuca            -      -      3     3      3
Gyps africanus                -      1      -     -      10
Gyps rueppellii               -      -      -     -      -
Gyps sp.                      -      -      -     -      -
Hirundo rustica               -      -      -     -      -
Hirundo senegalensis          -      2     17     4      4
Hoplopterus spinosus          -      -      -     -      -
Lagonosticta senegala         -      -      1     -      -
Laniarius barbarus            -      -      -     -      -
Macronyx croceus              -      -      -     -      -
Mirafra cantillans            -      -      -     -      -
Necrosyrtes monachus          -      -      -     -      -
Oena capensis                 -      -      -     -      1
Otus leucotis                 -      -      -     -      -
Passer griseus                -      -      -     -      -
Passer luteus                 -      -      -     -      -
Ploceus cucullatus            -      -      -     -      -
Polyboroides typus            -      -      -     -      -
Psittacula krameri            -      4      -     1      -
Pterocles sp.                 -      -      -     2      1
Riparia riparia               -      -      -     -     125
Serinus leucopygius           -      8      -     -      -
Spiloptila clamans            -      -      -     -      -
Sporopipes frontalis          -      1      -     -      -
Streptopelia decipiens        -      -      -     -      -
Streptopelia senegalensis     9      17    23     8      16
Streptopelia sp.              -      -      -     -      -
Streptopelia vinacea          8      7      9     7      6
Sylvia sp.                    -      -      -     -      -
Torgos tracheliotus           -      -      -     -      -
Uraeginthus bengalus          -      -      1     -      -
Urocolius macrourus           -      -      -     -      -
Vanellus senegallus           -      -      -     -      -
Vidua orientalis
unidentified species          1

Total                         22     47    81     27    177

Acridivorous

Bubalornis albirostris       457    703    214   149     94
Bubulcus ibis                 -      -      -     -      1
Bucorvus abyssinicus          -      -      -     -      -
Centropus senegalensis        -      -      -     -      -
Chelictinia riocourii         -      -      -     -      -
Ciconia ciconia               1      -      -     -      -
Circus aeruginosus            6      11    29     11     19
Circus pygargus               11     24    37     19     18
Cisticola juncidis            35     26    52     40     77
Cisticola sp.                 -      -      -     1      7
Coracias abyssinica           2      8      4     14     15
Cursorius temminckii          -      -      -     -      -
Elanus caeruleus              -      -      -     -      -
Eupodotus savilei             3      5     10     9      4
Falco naumanni                11     10     7     3      4
Halcyon senegalensis          12     12    13     3      2
Lamprotornis caudatus         6      8      6     2      10
Lamprotornis chalybaeus       -      -      -     -      -
Lanius meridionalis           -      -      -     -      -
Lanius senator                -      1      1     1      -
Leptoptilos crumeniferus      -      -      -     -      -
Macronyx croceus              -      -      -     -      -
Merops albicollis             47    160    78     39     79
Milvus migrans                -      -      -     -      -
Mirafra cantillans            28     44    55     40     24
Motacilla flava               -      -      -     -      -
Myrmecocichla aethiops        -      -      -     -      -
Neotis denhami                -      -      -     -      -
Oenanthe oenanthe             -      -      -     -      -
Oenanthe sp.                  -      -      -     -      -
Passer griseus                23     36    40     33     14
Ploceus cucullatus           118    373    89     26    112
Ploceus sp.                   -      -      -     -      -
Ploceus velatus               60     52    53     46     85
Prinia sp.                    -      1      2     -      3
Prinia subflava               -      -      -     -      -
Spreo pulcher                 -      -      -     -      -
Tchagra senegala              2      -      5     5      7
Tockus erythrorhynchus        4      8      6     3      2
Tockus nasutus                -      -      1     -      2
Turnix sylvatica              -      -      -     -      -
Upupa epops                   1      -      -     -      -
Vanellus tectus               41     51    43     30     64
Total                        868    1533   745   474    643

                              Number of days after treatment

Scientific Name               6     9     12     15     18

nonacridivorous

Anthus sp.                    -     -     -      -      -
Apus affinis                  -     -     -      -      -
Apus apus                     -     -     -      -      -
Aquila rapax                  -     -     -      -      -
Ardea cinerea                 -     1     -      2      4
Asio flammeus                 4     -     -      -      -
Bubalornis albirostris        -     -     -      -      -
Buphagus africanus            3     7     9      12     12
Calandrella brachydactyla     -     -     -      -      -
Camaroptera brachyura         -     -     -      -      -
Cercotrichas podobe           -     -     -      -      -
Ciconia nigra                 -     -     2      -      -
Cinnyris pulchellus           -     -     1      -      -
Circaetus beaudouini          -     -     -      -      -
Circaetus cinereus            1     -     -      -      -
Circaetus gallicus            3     7     7      8      13
Corvus albus                  -     -     -      -      -
Crinifer piscator             -     -     -      -      -
Delichon urbica               2    12     3      3      -
Eremopterix leucotis          4     6     3      10     20
Eremopterix nigriceps         -     -     -      -      -
Euodice cantans               -     -     1      -      -
Euplectes franciscanus        -     6     2      2      -
Falco ardosiaceus             1     -     -      -      1
Falco chicquera               -     1     -      -      -
Falco sp.                     -     -     -      2      -
Ficedula hypoleuca            1     -     -      1      -
Gyps africanus                -     -     2      2      8
Gyps rueppellii               9     4     9      7      -
Gyps sp.                      -     -     -      -      -
Hirundo rustica               -     -     -      -      -
Hirundo senegalensis          2     3     2      3      10
Hoplopterus spinosus          -     -     -      -      -
Lagonosticta senegala         -     -     -      -      -
Laniarius barbarus            -     -     -      -      -
Macronyx croceus              -     -     -      -      -
Mirafra cantillans            -     -     -      -      -
Necrosyrtes monachus          -     -     -      -      -
Oena capensis                 -     1     4      1      -
Otus leucotis                 -     -     -      -      1
Passer griseus                -     -     -      -      -
Passer luteus                 -     -     -      -      -
Ploceus cucullatus            -     -     -      -      -
Polyboroides typus            1     -     -      -      1
Psittacula krameri            4    20     18     19     23
Pterocles sp.                 2     7     6      6      5
Riparia riparia               7    10     -      7      -
Serinus leucopygius           -     -     -      -      -
Spiloptila clamans            -     -     -      -      -
Sporopipes frontalis          -     -     -      -      -
Streptopelia decipiens        -     -     -      -      -
Streptopelia senegalensis    29    40     49     64     68
Streptopelia sp.              -     -     -      -      2
Streptopelia vinacea          5    11     10     15     15
Sylvia sp.                    -     -     -      -      -
Torgos tracheliotus           -     -     -      -      -
Uraeginthus bengalus          2     1     4      1      2
Urocolius macrourus           -     -     -      -      6
Vanellus senegallus           -     -     -      -      -
Vidua orientalis
unidentified species

Total                        80    137   132    165    191

Acridivorous

Bubalornis albirostris       127   101   121    204    156
Bubulcus ibis                 -     3     -      -      15
Bucorvus abyssinicus          -     2     -      -      -
Centropus senegalensis        1     4     -      2      -
Chelictinia riocourii         -     -     -      -      -
Ciconia ciconia               -     -     -      -      -
Circus aeruginosus           24    22     31     41     37
Circus pygargus              28    33     42     34     36
Cisticola juncidis           101   155   169    200    168
Cisticola sp.                 3     2     3      -      1
Coracias abyssinica          24    49     57     46     49
Cursorius temminckii          -     -     -      -      2
Elanus caeruleus              -     -     -      -      -
Eupodotus savilei             9     9     10     5      6
Falco naumanni                2     3     5      -      3
Halcyon senegalensis          2    13     11     3      -
Lamprotornis caudatus         4    13     16     7      18
Lamprotornis chalybaeus       -     -     -      -      -
Lanius meridionalis           -     -     -      -      -
Lanius senator               19    30     30     27     19
Leptoptilos crumeniferus      1     -     -      -      -
Macronyx croceus              -     -     -      -      -
Merops albicollis            18    25     -      -      -
Milvus migrans                -     -     -      -      -
Mirafra cantillans           68    118   232    136    104
Motacilla flava               -     -     -      -      -
Myrmecocichla aethiops        -     -     -      -      -
Neotis denhami                2     -     -      -      -
Oenanthe oenanthe             -     3     -      2      8
Oenanthe sp.                  -     -     -      -      -
Passer griseus               12    76     49     49    105
Ploceus cucullatus           43    105    3      -      88
Ploceus sp.                   -     2     -      -      -
Ploceus velatus              82    68     89    180     81
Prinia sp.                   22    10     12     6      7
Prinia subflava               -     -     -      -      -
Spreo pulcher                 2     -     -      -      3
Tchagra senegala             10     6     19     16     19
Tockus erythrorhynchus        -     7     -      1      1
Tockus nasutus               49    33     82     21     58
Turnix sylvatica              -     -     -      -      -
Upupa epops                   -     -     -      3      -
Vanellus tectus              73    49     63     50     52
Total                        726   941   1044   1033   1036

                             Number of days after treatment

Scientific Name               47     74    109    137

nonacridivorous

Anthus sp.                    -      -      -      6
Apus affinis                  -      12     11     10
Apus apus                     -      -      -      -
Aquila rapax                  1      -      -      -
Ardea cinerea                 3      -      1      -
Asio flammeus                 -      -      -      -
Bubalornis albirostris       288    116    489     81
Buphagus africanus            10     13     17     3
Calandrella brachydactyla     -      -      -      10
Camaroptera brachyura         -      -      -      -
Cercotrichas podobe           1      -      -      -
Ciconia nigra                 -      -      -      -
Cinnyris pulchellus           -      14     -      2
Circaetus beaudouini          -      -      -      -
Circaetus cinereus            -      -      -      -
Circaetus gallicus            14     4      14     1
Corvus albus                  -      -      2      1
Crinifer piscator             -      -      -      -
Delichon urbica               -      -      -      10
Eremopterix leucotis          62     62     81    208
Eremopterix nigriceps         -      -      18     26
Euodice cantans               -      -      -      -
Euplectes franciscanus        -      -      -      -
Falco ardosiaceus             -      -      -      -
Falco chicquera               -      -      -      -
Falco sp.                     -      -      -      -
Ficedula hypoleuca            -      -      -      -
Gyps africanus                6      -      5      8
Gyps rueppellii               -      -      10     -
Gyps sp.                      28     22     20     24
Hirundo rustica               -      -      -      -
Hirundo senegalensis          -      -      5      -
Hoplopterus spinosus          -      4      -      -
Lagonosticta senegala         -     150    128    176
Laniarius barbarus            1      -      -      -
Macronyx croceus              -      -      -      -
Mirafra cantillans            59     39    199    157
Necrosyrtes monachus          1      -      -      -
Oena capensis                 4      7      7      8
Otus leucotis                 -      -      -      -
Passer griseus                42     67     8      1
Passer luteus                244    1210   1958   1677
Ploceus cucullatus            97    144     26     -
Polyboroides typus            1      -      -      -
Psittacula krameri            27     26     14     8
Pterocles sp.                 29     -      -      -
Riparia riparia               -      -      21     -
Serinus leucopygius           -      -      -      -
Spiloptila clamans            -      -      -      -
Sporopipes frontalis          -      -      -      -
Streptopelia decipiens        -      -      1      -
Streptopelia senegalensis     37     52     27     33
Streptopelia sp.              -      -      2      -
Streptopelia vinacea          28     25     20     12
Sylvia sp.                    2      -      -      -
Torgos tracheliotus           -      -      1      -
Uraeginthus bengalus          1      -      -      -
Urocolius macrourus           -      -      -      -
Vanellus senegallus           -      -      -      -
Vidua orientalis                                   2
unidentified species          22     5      4      -

Total                        1008   1972   3089   2464

Acridivorous

Bubalornis albirostris        -      -      -      -
Bubulcus ibis                 10     53    1872   418
Bucorvus abyssinicus          -      -      -      -
Centropus senegalensis        1      9      -      -
Chelictinia riocourii         -      -      -      -
Ciconia ciconia              1634   400     -      -
Circus aeruginosus            18     8      3      2
Circus pygargus               87     46    124    139
Cisticola juncidis            46     22     14     2
Cisticola sp.                 -      -      -      5
Coracias abyssinica           46    118    148    157
Cursorius temminckii          -      -      2      2
Elanus caeruleus              5      -      -      -
Eupodotus savilei             8      -      1      -
Falco naumanni               1122   123    592    198
Halcyon senegalensis          5      -      -      -
Lamprotornis caudatus         28     23     17     5
Lamprotornis chalybaeus       5      1      65     53
Lanius meridionalis           -      -      -      4
Lanius senator                28     35     54     51
Leptoptilos crumeniferus      1      -      -      -
Macronyx croceus              -      -      -      -
Merops albicollis             -      -      -      -
Milvus migrans                17     -      -      1
Mirafra cantillans            -      -      -      -
Motacilla flava               -      -      10     -
Myrmecocichla aethiops        -      10     1      -
Neotis denhami                -      -      -      -
Oenanthe oenanthe             27     17     39     49
Oenanthe sp.                  -      -      2      -
Passer griseus                -      -      -      -
Ploceus cucullatus            -      -      -      -
Ploceus sp.                   -      -      -      -
Ploceus velatus               -      -      -      -
Prinia sp.                    -      -      -      -
Prinia subflava               -      -      -      -
Spreo pulcher                 4      8      9     750
Tchagra senegala              -      -      -      -
Tockus erythrorhynchus        22     18     15     27
Tockus nasutus                21     12     17     49
Turnix sylvatica              -      5      1      -
Upupa epops                   1      3      4      5
Vanellus tectus               95    142    192    203
Total                        3231   1053   3182   2120

                             Number of days
                             after treatment

Scientific Name               167      233     Total

nonacridivorous

Anthus sp.                     2        -        8
Apus affinis                   -        -       33
Apus apus                      -        -       17
Aquila rapax                   -        -        1
Ardea cinerea                  -        -       15
Asio flammeus                  -        -        4
Bubalornis albirostris        212       56     1242
Buphagus africanus             7        17      110
Calandrella brachydactyla      -        2       12
Camaroptera brachyura          1        1        4
Cercotrichas podobe            -        8        9
Ciconia nigra                  -        -        2
Cinnyris pulchellus            -        8       19
Circaetus beaudouini           -        -        1
Circaetus cinereus             -        -        1
Circaetus gallicus             1        1       73
Corvus albus                   -        4        7
Crinifer piscator              1        2        3
Delichon urbica                6        2       45
Eremopterix leucotis          245      251      952
Eremopterix nigriceps          48       -       92
Euodice cantans                1        -        2
Euplectes franciscanus         -        -       20
Falco ardosiaceus              -        -        5
Falco chicquera                -        -        6
Falco sp.                      -        2        4
Ficedula hypoleuca             -        -       11
Gyps africanus                 -        -       42
Gyps rueppellii                -        -       39
Gyps sp.                       25       21      140
Hirundo rustica                12       -       12
Hirundo senegalensis           2        4       58
Hoplopterus spinosus           -        -        4
Lagonosticta senegala          6        -       461
Laniarius barbarus             -        -        1
Macronyx croceus               4        -        4
Mirafra cantillans            233      268      955
Necrosyrtes monachus           -        -        1
Oena capensis                  6        10      49
Otus leucotis                  -        -        1
Passer griseus                 3        1       122
Passer luteus                 1032     5128    11249
Ploceus cucullatus             -        -       267
Polyboroides typus             -        -        3
Psittacula krameri             26       3       193
Pterocles sp.                  -        -       58
Riparia riparia                -        -       170
Serinus leucopygius            -        -        8
Spiloptila clamans             1        -        1
Sporopipes frontalis           -        -        1
Streptopelia decipiens         -        -        1
Streptopelia senegalensis      28       66      566
Streptopelia sp.               -        -        4
Streptopelia vinacea           5        13      196
Sylvia sp.                     -        -        2
Torgos tracheliotus            -        -        1
Uraeginthus bengalus           -        -       12
Urocolius macrourus            -        -        6
Vanellus senegallus            -        2        2
Vidua orientalis               -        -        2
unidentified species           -        1       33

Total                         1907     5871    17362

Acridivorous

Bubalornis albirostris         -        -      2326
Bubulcus ibis                 165      839     3376
Bucorvus abyssinicus           -        -        2
Centropus senegalensis         2        -       19
Chelictinia riocourii          -        3        3
Ciconia ciconia                -        -      2035
Circus aeruginosus             6        -       268
Circus pygargus                48       16      742
Cisticola juncidis             -        -      1107
Cisticola sp.                  23       25      70
Coracias abyssinica            93       75      905
Cursorius temminckii           4        5       15
Elanus caeruleus               -        -        5
Eupodotus savilei              6        -       85
Falco naumanni                 95       6      2184
Halcyon senegalensis           1        1       78
Lamprotornis caudatus          6        -       169
Lamprotornis chalybaeus       128       62      314
Lanius meridionalis            2        -        6
Lanius senator                 45       12      353
Leptoptilos crumeniferus       -        -        2
Macronyx croceus               3        -        3
Merops albicollis              -        62      508
Milvus migrans                 -        -       18
Mirafra cantillans             -        -       849
Motacilla flava                -        -       10
Myrmecocichla aethiops         -        83      94
Neotis denhami                 -        -        2
Oenanthe oenanthe              16       5       166
Oenanthe sp.                   -        -        2
Passer griseus                 -        -       437
Ploceus cucullatus             3        -       960
Ploceus sp.                    -        -        2
Ploceus velatus                -        -       796
Prinia sp.                     -        -       63
Prinia subflava                -        4        4
Spreo pulcher                 459       29     1264
Tchagra senegala               -        -       89
Tockus erythrorhynchus         22       9       145
Tockus nasutus                 17       30      392
Turnix sylvatica               -        -        6
Upupa epops                    2        1       20
Vanellus tectus               165      186     1499
Total                         1311     1453    21393


Submitted February 7, accepted June 6, 2010

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* Paper delivered as part of a symposium: Integrated pest management for locusts and grasshoppers: are alternatives to chemical pesticides credible? Antalya, Turkey, 21-25 June 2009.

Wim C. Mullie And Youssoupha Gueye

(WCM) Agriculture Directorate, Ministry of Agriculture, P.O. Box 486, Dakar, Senegal. E-mail: wim_sen@yahoo.fr (YG) Crop Protection Directorate, Ministry of Agriculture, P.O. Box 20054, Dakar, Senegal.
Table 1. Information on body mass, (corrected) field metabolic rates
(FMR), origin, detection probabilities, effective strip width (ESW)
and model parameters used in calculations of species considered as
acridivorous during at least a part of the study period.

                                    Body             corr.
Scientific name                n    Mass     FMR      FMR     origin

Bubalornis albirostris       405    75.4    199.4    269.4      A
Bubulcus ibis                144     335    550.5    743.9      A
Bucorvus abyssinicus           1    4000   2979.8   4026.8      A
Centropus senegalensis        14     170    346.8    468.7      A
Chelictinia riocourii                110    257.9    348.5      A
Ciconia ciconia               28    3473   2706.5   3657.4      P
Circus aeruginosus           763   627.5    844.0   1140.6      P
Circus pygargus                    315.5    528.5    714.1      P
Cisticola juncidis           662     7.7     42.2     57.0      A
Cisticola sp.                        7.7     42.2     57.0      A
Coracias abyssinica          542     114    264.2    357.0      A
Cursorius temminckii           3    68.5    186.8    252.4      A
Elanus caeruleus               3     240    438.6    592.8      A
Eupodotus savilei             78     615    832.6   1125.1      A
Falco naumanni               422   152.5    322.1    435.3      P
Halcyon senegalensis          56    56.9    164.6    222.4      A
Lamprotornis caudatus         74     121    275.1    371.8      A
Lamprotornis chalybaeus       19     100    241.7    326.6      A
Lanius meridionalis            2    65.5    181.2    244.8      A
Lanius senator               269    31.9    111.0    150.0      P
Leptoptilos crumeniferus       2    6325   4071.1   5501.5      A
Macronyx croceus                    47.6    145.8    197.0      A
Merops albicollis            143    24.2     92.0    124.3      A
Milvus migrans                11     704    912.8   1233.5      P
Mirafra cantillans           655    18.7     77.1    104.3      A
Motacilla flava                5    17.6     74.0    100.0      P
Myrmecocichla aethiops         7    56.6    164.0    221.6      A
Neotis denhami                 1    4120   3040.4   4108.7      A
Oenanthe oenanthe                   23.2     89.3    120.7      P
Oenanthe sp.                 111    23.2     89.3    120.7      P
Passer griseus               243    28.1    101.8    137.6      A
Ploceus cucullatus                  37.5    123.9    167.4      A
Ploceus sp.                  420    37.5    123.9    167.4      A
Ploceus velatus                     24.2     92.0    124.3      A
Prinia subflava.              54       9     46.9     63.4      A
Spreo pulcher                 34    64.2    178.7    241.5      A
Tchagra senegala              88    53.9    158.6    214.4      A
Tockus erythrorhynchus        65     146    312.7    422.6      A
Tockus nasutus               106     208    397.9    537.7      A
Turnix sylvatica               4    23.2     89.3    120.7      A
Upupa epops                   16    51.9    154.6    208.9      P
Vanellus tectus              417   112.5    261.8    353.8      A

                                          ESW (m)
                                         95% conf.
                                            int.

Scientific name            Detect.   avg.   min.   max.

Bubalornis albirostris      ind.      61     55     69
Bubulcus ibis               ind.     316    274    364
Bucorvus abyssinicus          3      243    227    261
Centropus senegalensis        2       71     68     75
Chelictinia riocourii         1      243    227    261
Ciconia ciconia               3      243    227    261
Circus aeruginosus          ind.     236    222    252
Circus pygargus             ind.     236    222    252
Cisticola juncidis          ind.      20     19     22
Cisticola sp.               ind.      20     19     22
Coracias abyssinica         ind.     102     93    112
Cursorius temminckii          2       71     68     75
Elanus caeruleus              3      243    227    261
Eupodotus savilei             2       71     68     75
Falco naumanni              ind.     233    214    255
Halcyon senegalensis        ind.      59     40     87
Lamprotornis caudatus       ind.      80     64     99
Lamprotornis chalybaeus       2       71     68     75
Lanius meridionalis           2       71     68     75
Lanius senator              ind.     106     91    123
Leptoptilos crumeniferus      3      243    227    261
Macronyx croceus              1       36     34     37
Merops albicollis           ind.      43     38     49
Milvus migrans                3      243    227    261
Mirafra cantillans          ind.      33     31     34
Motacilla flava               1       36     34     37
Myrmecocichla aethiops        2       71     68     75
Neotis denhami                3      243    227    261
Oenanthe oenanthe           ind.      54     47     62
Oenanthe sp.                ind.      54     47     62
Passer griseus              ind.      35     30     40
Ploceus cucullatus          ind.      38     34     42
Ploceus sp.                 ind.      38     34     42
Ploceus velatus             ind.      38     34     42
Prinia subflava.              1       36     34     37
Spreo pulcher               ind.      61     47     79
Tchagra senegala            ind.      53     38     74
Tockus erythrorhynchus      ind.      87     68    112
Tockus nasutus              ind.      36     23     57
Turnix sylvatica              1       36     34     37
Upupa epops                   2       71     68     75
Vanellus tectus             ind.      67     59     75

                               details of model applied

Scientific name            type   interval    truncation (m)

Bubalornis albirostris      HR     manual              1000
Bubulcus ibis               HN     manual              2000
Bucorvus abyssinicus        HR     manual              1175
Centropus senegalensis      HN     manual               375
Chelictinia riocourii       HR     manual              1174
Ciconia ciconia             HR     manual              1175
Circus aeruginosus          HN    automatic               -
Circus pygargus                                           -
Cisticola juncidis          HN     manual               140
Cisticola sp.
Coracias abyssinica         HR    automatic               -
Cursorius temminckii        HN     manual               375
Elanus caeruleus            HR     manual              1175
Eupodotus savilei           HN     manual               375
Falco naumanni              HN     manual              2000
Halcyon senegalensis        HR    automatic               -
Lamprotornis caudatus       HN     manual               600
Lamprotornis chalybaeus     HN     manual               375
Lanius meridionalis         HN     manual               375
Lanius senator              HR     manual               200
Leptoptilos crumeniferus    HR     manual              1175
Macronyx croceus            HR     manual               105
Merops albicollis           HR    automatic             200
Milvus migrans              HR     manual              1175
Mirafra cantillans          HN    automatic               -
Motacilla flava             HR     manual               105
Myrmecocichla aethiops      HN     manual               375
Neotis denhami              HR     manual              1175
Oenanthe oenanthe           HN    automatic             125
Oenanthe sp.
Passer griseus              HR    automatic               -
Ploceus cucullatus
Ploceus sp.                 HR     manual               250
Ploceus velatus
Prinia subflava.            HR     manual               105
Spreo pulcher               HN     manual               170
Tchagra senegala            HR    automatic               -
Tockus erythrorhynchus      HR    automatic               -
Tockus nasutus              HR     manual               800
Turnix sylvatica            HR     manual               105
Upupa epops                 HN     manual               375
Vanellus tectus             HR    automatic               -

n: number of observations (not necessarily number of birds; some
species occur in groups). Body mass: fresh body mass (g) (cf.
Dunning 1993). FMR: FMR in kJ/day = 10.5 x body mass
[(g).sup.0.681] (according to Nagy 2005). corr FMR: FMR corrected
for digestibility [= (FMR/74) x 100)] (According to Petersen et al.
2008). origin: A = Afrotropical, P = Palaearctic. detect.
Detect[ability]: ind. = individual. ESW could be calculated. 1 =
species with low detectability; 2 = species with medium
detectability; 3 = species with high detectability (see text for
details). ESW: Effective Strip Width (Buckland et al. 1993, Thomas
et al. 2006), see under Statistics. Energy content grasshopper 22
kJ/g DW (Petersen et al. 2008); % water in grasshopper 71.6
(Petersen et al. 2008). Type: HR = Hazard Rate model, HN = Half
Normal with Cosine Expansion model.

Table 2. Species composition of grasshoppers captured in the field
by sweep-net sampling and found as prey remains in regurgitated
pellets of Montagu's Harriers, collected in night roosts, at Khelcom
between January and March 2009.

                                                     January

                                      Wet        field    M. Harrier
Scientific Name                    Weight (g)   n=2655      n=1628

Acanthacris ruficornis citrina        3.5          -          -
Hieroglyphus daganensis               3.41         -          -
Ornithacris cavroisi                  2.66       15.07      25.55
Truxalis johnstoni                    1.57       0.26         -
Truxalis sp.                          1.57         -         0.06
Acridoderes strenuus                  1.07         -          -
Acrida bicolor                        0.91       0.45         -
Acrida sp.                            0.91       0.26         -
Acorypha clara                        0.9        18.57      61.18
Heteracris annulosa                   0.77         -          -
Diabolocatantops axillaris            0.73        4.6       11.55
Metaxymecus gracilipes                0.64       0.45         -
Acorypha picta                        0.57       5.46        1.66
Oedaleus senegalensis                 0.53       0.23         -
Catantops stramineus                  0.5        1.13         -
Harpezocatantops stylifer             0.3        0.56         -
Chrotogonus senegalensis              0.29       1.51         -
Cryptocatantops haemorrhoidalis       0.23       0.11         -
Pyrgomorpha vignaudii                 0.19       19.47        -
Zacompsa festa                        0.18         -          -
Pyrgomorpha cognata complex           0.09       19.66        -
Acrotylus blondeli                    0.07       11.19        -
Unidentified species                             1.02         -

Total                                             100        100

                                         February

                                    field    M. Harrier
Scientific Name                    n=3037       n=971

Acanthacris ruficornis citrina        -           -
Hieroglyphus daganensis               -          0.1
Ornithacris cavroisi                10.41       25.75
Truxalis johnstoni                    -           -
Truxalis sp.                          -           -
Acridoderes strenuus                  -          0.1
Acrida bicolor                        -           -
Acrida sp.                            -           -
Acorypha clara                      14.55       57.16
Heteracris annulosa                   -           -
Diabolocatantops axillaris          7.08        15.45
Metaxymecus gracilipes              0.82          -
Acorypha picta                      7.41        1.34
Oedaleus senegalensis                 -           -
Catantops stramineus                0.86          -
Harpezocatantops stylifer           1.98          -
Chrotogonus senegalensis            2.54          -
Cryptocatantops haemorrhoidalis     3.79         0.1
Pyrgomorpha vignaudii               17.42         -
Zacompsa festa                        -           -
Pyrgomorpha cognata complex         21.24         -
Acrotylus blondeli                  11.43         -
Unidentified species                0.49          -

Total                                100         100

                                          March

                                    field    M. Harrier
Scientific Name                    n=3232      n=1632

Acanthacris ruficornis citrina      0.09        0.06
Hieroglyphus daganensis               -           -
Ornithacris cavroisi                9.13        22.61
Truxalis johnstoni                    -           -
Truxalis sp.                          -         0.18
Acridoderes strenuus                  -         0.31
Acrida bicolor                        -           -
Acrida sp.                            -           -
Acorypha clara                      15.16       65.32
Heteracris annulosa                  2.2          -
Diabolocatantops axillaris          5.85        8.88
Metaxymecus gracilipes                -           -
Acorypha picta                      6.13        2.27
Oedaleus senegalensis                 -           -
Catantops stramineus                1.58          -
Harpezocatantops stylifer           3.96          -
Chrotogonus senegalensis            0.46          -
Cryptocatantops haemorrhoidalis     3.47        0.31
Pyrgomorpha vignaudii               20.2        0.06
Zacompsa festa                        -           -
Pyrgomorpha cognata complex         21.6          -
Acrotylus blondeli                  10.18         -
Unidentified species                  -           -

Total                                100         100
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Author:Mullie, Wim C.; Gueye, Youssoupha
Publication:Journal of Orthoptera Research
Article Type:Report
Geographic Code:6SENE
Date:Jan 1, 2010
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