Species diversity and richness of wild birds in Dagona-Waterfowl Sanctuary, Nigeria.
Wetlands are of important ecological significance in the tropical region, which serves as a major link between the natural resource management and agricultural practices. They are a store house or hot-spot for the conservation of important species that rural inhabitants mostly depend upon for a source of protein, while at the same time serving deep interests of the conservationists for protection. In all the three types of wetlands (marine/coastal, inland or man-made), the most significant point of reference is water management. Therefore, a wetland or riparian ecosystem is a servicing point for diverse species of animals (fishes, birds, antelopes, primates and carnivores) that need water either for drinking, wallowing or abode .
Wetlands are unique biotic communities involving diverse plants and animals that are adapted to shallow and often dynamic water regimes. The Convention on Wetlands of International Importance, commonly called the "Convention on Wetlands" (or the RAMSAR convention), signed in Ramsar, Iran in 1971, defines wetlands as "areas of marsh, fern, peat land or water, whether natural or artificial, temporary or permanent, with water that is static or flowing, fresh, brackish or salt, including areas of marine water, the depth of which at low tide does not exceed six meters". In addition, the Convention provides that wetlands "may incorporate riparian and coastal zones adjacent to the wetlands and islands or bodies of marine water deeper than six meters at low tide lying within the wetland" . There are also man-made wetlands such as fish and shrimp ponds, farm ponds, irrigated agricultural land, salt pans, reservoirs, gravel pits, sewage pits, sewage farms, and canals .
Although wetlands occupy a small portion of the earth's land area, they are very important in the biosphere. Over geologic time, wetland environments produced the vegetation that has been converted into coal. Salt water marshes are important breeding areas for many oceanic animals and many invertebrates. Dominant animal species in fresh water wetlands include many species of insects, birds, and amphibians; few mammals are also included this biome .
Wetlands are known for their abundance of birds. The use of wetlands and their resources is widespread among many diverse bird taxa of the world. Avian adaptation to utilize wetlands and other aquatic systems are diverse and include anatomical, morphological, behavioral changes. Anatomically, they include designs for diving and swimming, such as body compression to increase gravity, or adaptation for plunge diving from great heights . Respiratory physiology differs dramatically in those bird species that engage in long period of time deep diving into the water body . Morphological adaptations include bills that strain, peck, spear, store and grab, and feet that allow swimming, diving, walking on mudflat, wadding or grabbing and holding fish. Not only do body parts differ in general form, but also size of bills, legs, and flight patterns differ across a gradient of wetland edges . As a result of these adaptations, birds are better equipped as a group to exploit wetland resources and are often used as indicators of conditions within a wetland ecosystem .
In Nigeria, the Hadeija-Nguru Lake (Marma channel) complex is a designated Ramsar site. The surface area enclosed is about 58,100 hectares, with an elevation of 340345m, located northeastern Nigeria (10[degrees] 22' N, 012[degrees] 46' E), with two-third of this site in Jigawa State and one-third in Yobe State. The Nguru Lake is a good representation of a natural or near-natural wetland, which embodies all the diverse flora and fauna of both the Sahel and the Sudan savanna in a single limited location. It regularly supports more than 20,000 water birds and is also a wintering ground for many palearctic migrant birds. A total of 377 wetland bird species have been recorded in the wetland and the total numbers of water birds recorded during the January African Water bird census counts were 259,769 in 1995; 201,133 in 1996 and 324,510 in 1997 . The aim of this study was to assess species diversity and richness of wild birds and to provide a species list in Dagona Waterfowl Sanctuary. Birds are good environmental indicators, revealing the state of the ecosystems such as wetland. They also serve as dispersal agents in transferring nutrients and spores from one place to another during their migration and local movements .
THE STUDY AREA
The Dagona Wildlife Sanctuary is located within the Bade-Nguru Wetland Sector. The Sanctuary covers an area of 938sq.km and comprises the 1966 legislated Bade Native Authority Gogoram and Zurgum Baderi Forest Reserves. It is situated southwest of Bade and Jakusko local government areas of Yobe State. It is located between latitudes 12[degrees]13' and 13[degrees]00' and longitudes 10[degrees]00' and 11[degrees]00' (Figure 1--Map of Nigeria showing location of the Sectors). Dagona Waterfowl Sanctuary is significant to the internationally assisted conservation effort to protect the palaearctic migrant birds. It is open Sudan/scrub Sahelian vegetation, though a small part of the wetland is covered with water all year round yielding support for water birds and other wildlife found in that area.
The sanctuary is bordered by some villages and the main occupation is pastoral farming with high incidence of grazing by the Fulani community. The Waterfowl sanctuary is among the Hadeija-Nguru Wetlands while the management of the sanctuary is under the jurisdiction of the Chad Basin National Park. The sanctuary is under multiple-use management, and there is no free access to wild resources (wild animals, fish, birds). However, grazing and collection of wild resources are practiced by the local population illegally, and there is, therefore, need for more strict enforcement of laws .
[FIGURE 1 OMITTED]
MATERIALS AND METHODS
The Line Transect method was used to survey birds. This method proved most efficient in terms of data collection per unit effort. This census involves an observer moving slowly along the routes and recording all birds detected on either side of the route. The length of transects depends on the type of survey but is usually constrained by accessibility and thus may not be fixed. Line transects are often used to collect data in large open areas and is more efficient than point counts as one tends to record more birds per unit time .
Surveys were carried out at three different lakes (Gatsu, Mariam and Oxbow, referred to as sites 1 to 3) in 2009 using the line transect method. A Garmin[TM] 12 Geographic Positioning System (GSP) was used to mark each point. At each site, bird observation was carried out twice daily. Morning between 0630hrs and 1000hrs and evening, between 1600hrs and 1800hrs by walking slowly along transects and making observations. The length of each transect was one kilometer and was subdivided into 50meters sub-sections to aid data collection and habitat measurements. At each site, transects were placed 100m apart.
Birds were counted as bird seen and heard and birds in flight were also recorded. A pair of binoculars with magnification 7x 50 was used in identification of birds visually alongside a field guide .
The data were tested with the Kolmogorov- Smirnov to determine whether or not they were normally distributed while parametric tests were applied for all data.
Birds' diversity was calculated using the Shannon-Weiner Diversity Index, H
H = -[s.summation over (i=1)] [P.sub.i] ln[P.sub.i]
[P.sub.i] = Proportion of individual species
S = Total number of species of the community (number of bird seen and heard).
Average bird diversity was calculated by getting a mean of the replicated surveys of bird diversity at each point for mornings and evenings for all sites. One-way ANOVA was used to determine if the differences in mean bird species diversity across sites were significant. A post hoc test was carried out to ascertain the level of variance in bird species diversity at the three sites.
The means of vegetation variables were calculated. Pearson's correlation was used to determine if there were significant associations between habitat variables and mean bird diversity. Using the bird diversity as the dependent variable, the Generalized Linear Model (GLM) was used to test if vegetation variables had any relationship with bird diversity. Model equation is given as:
Y = [b.sub.0] + [b.sub.1]x
Where Y = dependent variable
[b.sub.0] = corrected [R.sup.2] , [b.sub.1] = independent variables and x =error
The results of this study showed that bird species diversity was normally distributed at all the sites (Table 2). A one-way ANOVA showed that bird diversity varied significantly (P<0.05) between the three sites. Site 2 (Maram) had the highest diversity (2.74) compared to site 1 (Gastu) (1.84) and site 3 (Oxbow) (1.62). Thus, site 2 had the highest diversity as indicated in Figure 2. Birds were more easily sighted and species easily identified; they were concentrated in the woodland forest ecosystem than in the riparian environment.
[FIGURE 2 OMITTED]
Bird species richness in the area was normally distributed among the three sites, (Table 3). There was a significant difference (P<0.05) within species richness at the three sites (Table 4). Site 1 had the highest species richness (16.36) compared to the other two sites 2 and 3 that gave 14.32 and 11.51 respectively.
[FIGURE 3 OMITTED]
Figure 3 showed that site 1(Gastu lake) had the highest number of bird species (16.36) as compared to site 2 (Maram lake) (14.32) and site 3(Oxbow lake) (11.51); site 3 had the least number of bird species.
Vegetation Distribution & Species Diversity
There was a significant relationship between vegetation densities and bird species diversity. As tree density increased, diversity of bird species decreasesd (figure 4). At tree density of 1.0 the bird species diversity recorded at evening was above 4,000; at 2.0 tree density the diversity of bird species was 2,500. It was noted that there was more human disturbance (anthropogenic activity) at the forested area of the lakes. Activities like firewood extraction collection, poaching, bush burning and forest fruit gathering were common. Likewise, more birds were recorded at evening time (>4,000 birds) than during the morning time (3,000 birds) within the vegetation area. This indicated greater bird activities at evening time before nest-roosting than early-morning hours' activity.
[FIGURE 4 OMITTED]
Checklist of Bird species in Dagona Waterfowl Sanctuary
A total of 135 bird species in 40 families were recorded during the survey (Table 5). Seventy-four percent were found in Gastu Lake, sixty-three percent in Maram Lake and seventy-one percent in Oxbow Lake. More bird species were recorded at disturbed areas (site 1) compared to least disturbed sites (2 and 3).
The majority of wetland birds observed during this study were resident species, migratory and palearctic bird species. Some of the palearctic species recorded included the Yellow Wagtail, the Warblers, Northern Shoveler, the Sandpipers and the migrants and residents were also of a considerable number. The species that were winter migrants used the wetlands area for resting and other activities while waiting for favorable condition in their home range. During this time, they store enough fat for the journey back to Europe . Migrant species observed during the study were fairly few, especially the Family Accipitridae which were observed to have moved down South. The period of the study favoured the level of water that is deep enough for wetland birds, especially the water birds to carry out daily activities such as feeding, resting, nesting and predator escape. An important observation is that the bird diversity and abundance (richness) varies across sites and this was influenced by various factors, some of which included: the fact that wetlands provide food for birds in form of plants, vertebrates and invertebrates. Some of them forage for food in wetland soil, some in the water column, and others use the dry landscape, along the streams. They may be affected by quality and quantity of food. Vegetarian birds (follivore) like the White-Faced Whistling duck are likely to be affected by quality of the vegetation as it was observed during this study. Birds that are commonly found at the riparian vegetation need more protein, less of other tannins and poisonous substances which are required by the carnivorous birds such as the herons and the storks. This is because it is the quality of food which is important to the species but not the quantity .
The extent to which wetland birds utilize wetland as cover and hiding areas depends and varies among wetland birds; the absence of such hiding cover may result in some species being scarce. Well vegetated wetlands seem attractive to wetland bird species .
The absence of a specific and proper nesting site may affect the abundance and diversity of wetland bird species. Ducks nest over the water, while the Spur-winged Goose nests on the sand bars as observed during the study, the Spur-winged Lapwing are on the lake shore as shore feeder. The Jacanas were observed in the vegetated part of the lake at the three sites and so were the lily trotters. The bird species found in wetlands need specific areas to carry out reproductive activities such as roosting and nesting .
This study revealed a positive relationship between percentage ground cover, shrub density and tree density to bird recorded. More birds were observed in areas with higher percentage of ground cover (disturbed sites) and shrub density (135 bird species) but fewer birds were observed as tree density increased (71 bird species). This observation indicated that some wetland birds used the trees as roosting site. This was observed with some species such as the Egrets, Ibises, Herons and Storks. These species were found during the survey on the bare ground feeding on the mudflats fish and other vertebrate. Thus, habitat has long been used as a predictor of bird species abundance, and each variety of birds has developed different preferences for habitat . Birds select vegetation variables according to the manner by which an individual habitat affects access to food, mates or its vulnerability to predators .
Bird communities are often referred to as an ideal indicator to monitor the ecological condition of any wetlands as they impact on all the trophic levels of an aquatic ecosystem. Dagona Waterfowl Sanctuary is a peculiar example of these bird communities. Aquatic ecosystems have significant impact on migratory birds. Birds carry out diverse ranges of ecological functions among vertebrates. As consumers, they help regulate populations of smaller animals they prey upon, disperse plant seeds, and pollinate flowering plants. As prey items, birds and bird eggs are consumed by a variety of larger predators. Birds also benefit humans by providing important ecosystem services such as regulating services by scavenging carcasses and waste, by controlling population of invertebrates and vertebrate pests, by pollinating and dispersing the seeds of plants; and supporting services by cycling nutrients. They served as indicators revealing the state of the wetland, as dispersal agents in transferring nutrients and spores from one wetland to another during migration and local movements .
Grazing, fishing and logging were the main illegal activities in the Dagona Waterfowl Sanctuary and this might be detrimental to bird species diversity in the long term. Fulani cattle grazers mostly invade the Sanctuary and fell trees to get leaves for their cattle. Several attempts by the authorities to curtail these activities were abortive. Studies have shown that selective logging can affect the diversity of bird species positively . This can be introduced in some parts of the sanctuary that are experiencing fewer disturbances of bird species at sustainable management level.
Bird diversity and abundance are normally distributed among the sites in Dagona Waterfowl Sanctuary and some species are more abundant than others. This is due to the fact that some parts were more disturbed than others as it was observed that Gastu and Oxbow lakes had more disturbance than the Maram lakes. Also, the communities around the Gastu and Oxbow lakes were more than those of Maram, which means reduced human disturbance on the habitat and the bird communities. A check-list of 135 avian composition was generated and it was found that habitat structure affects avian diversity and the species abundance in this study. Therefore, it was recommended that regular monitoring of the site should be carried out so as to control changes in the state of wetland especially on the resident and palearctic species. Thus, protection of this ecosystem (Dagona wetland Sanctuary) will ensure better protection of resource richness (water, soil, animals and plants) and thereby enable future sustainable utilization of the resources. If this ecosystem is under threat by humans and is not properly managed by policy makers, then it will send a serious signal on environmental viability of the region and invariably affect the general ecosystem productivity.
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Lammed G.A. (1) *
* Corresponding author email: firstname.lastname@example.org; email@example.com
(1) Associate Professor) Department of Wildlife and Ecotourism Management, Faculty of Agriculture and Forestry, University of Ibadan, Ibadan; Nigeria.
Table 1: One-Sample Kolmogorov Smirnov Test for species diversity of the sites Site Morning Evening Z-score N Sig. Gastu 0.6726 0.3680 18 2 0.7562 0.9992 Maram 0.52185 0.5928 10 10 0.8737 0.9482 Oxbow 0.5558 0.9047 33 15 0.9168 0.3862 Table 2: Least Significant Difference for Multiple Comparisons of Species Diversity (Dependent Variable) Mean Difference Std. (I) site (J) site (I-J) Error Sig. 1 2 -0.88419 0.173621 <0.0001 3 0.22575 0.135651 0.098056 2 1 0.884193 0.173621 <0.0001 3 1.109942 0.155255 3.05E-11 3 1 -0.22575 0.135651 0.098056 2 -1.10994 0.155255 <0.0001 95% Confidence (I) site Interval Lower Upper Bound Bound 1 -1.22711 -0.54128 -0.04217 0.493673 2 0.541275 1.22711 0.803299 1.416585 3 -0.49367 0.042174 -1.41659 -0.8033 Table 3: One-Sample Kolmogorov Smirnov Test for bird species richness in each site Site Morning Evening Z-score N Sig. Gastu 1.049485 0.368049 2 18 0.22 0.99 Maram 0.550998 0.654709 10 10 0.92 0.78 Oxbow 1.869643 0.810866 15 33 0.00 0.53 Table 4: Least Significant Difference for Multiple Comparisons of Species Richness (Dependent Variable) Mean Difference (I) site (J) site (I-J) Std. Error Sig. 1 2 2.047969481 2.503185 0.414506 3 4.850705329 1.955752 0.014178 2 1 -2.047969481 2.503185 0.414506 3 2.802735848 2.238395 0.212377 3 1 -4.850705329 1.955752 0.014178 2 -2.802735848 2.238395 0.212377 (I) site 95% Confidence Interval Lower Upper Bound Bound 1 -2.89605 6.99199 0.987916 8.713495 2 -6.99199 2.896051 -1.6183 7.223772 3 -8.71349 -0.98792 -7.22377 1.6183 Table 5: Checklist of Bird species in Dagona Waterfowl Sanctuary Family Scientific name Common name 1. Accipitridae Accipiter tachiro African goshawk Circus ranivorus African marsh harrier Accipitridae Bird of prey Elanus caeruleus Black-shouldered kite Melierax metabates Dark chanting goshawk Kaupifalco Lizard buzzard monogrammicus Circus ranivorus Marsh harrier Accipiter ovampensis Ovambo sparrowhawk Circus macrourus Pallid harrier Acccipiter badius Shikra 2. Alcedinidae Ceyx lecontei African dwarf kingfisher Halcyon leucocephala Grey-headed kingfisher Ceryle rudis Pied kingfisher 3. Ardeidae Egretta ardesiaca Black heron Bubulcus ibis Cattle egret Egretta alba Great egret Ardea cinerea Grey heron Egretta intermedia Intermediate egret Egretta garzetta Little egret Egretta garzetta Lesser egret Ardea purpurea Purple heron Ardeola ralloides Squacco heron 4. Anatidae Dendrocygna viduata White-faced whistling duck Anas querquedula Garganey Sarkidiornis Knob-billed duck melanotos Anas clypeata Northern shoveler Plectropterus Spur-winged goose gambensis 5. Alaudidae Galerida modesta Sun lark Eremopterix nigriceps Black-crowned sparrow lark Eremopterix leucotis Chestnut-backed sparrow lark Galerida cristata Crested lark 6. Bucerotidae Tokus camurus Red-billed hornbill Tokus nasutus African grey hornbill 7. Columbidae Streptopelia African collared dove hypopyrrha Streptopelia African mourning dove decipiens Turtur abyssinicus Black-billed wood dove Streptopelia spp Dove Streptopelia Laughing dove sensgalensis Oena capensis Namaqua dove Streptopelia vinacea Vinaceous dove Streptopelia Red-eyed dove semitorquata Columba guinea Speckled pigeon 8. Ciconiidae Anastomus African openbill lamelligerus stork Ciconia nigra Black stork Leptoptilos Marabou stork crumeniferus Anastomus Open-bill stork lamelligerus 9. Collidae Urocolius macrourus Blue-naped mousebird 10. Corvidae Corvus albus Pied crow 11. Coraciidae Coracias abbyssinicus Abyssian rollerS 12. Capitonidae Pogoniulus scolopaceus Yellow-fronted tinkerbird Lybius vieilloti Veillot barbet 13. Charadriidae Charadrius marginatus White-fronted plover Vanellus spinosus Spur-winged lapwing 14. Cuculidae Centropus sensgalensis Senegal coucal 15. Estrildidae Euodice cantans African silverbill Estrilda troglodytes Black rumped waxbill Amadina fasciatus Cut-throat Lagonosticta Senegal Red-billed firefinch Estrilda troglodytes Black-rumped waxbill Uraeginthus bengalus Red-cheeked cordon bleu Serinus leucopygius White rumped seedeater 16. Falconidae Falco ardosiaceus Grey kestrel 17. Jacanidae Actophilornis African jacana Africana Microparra capensis Lesserjacana 18. Laniidae Lanius meridionalis Southern grey Shrike 19. Malaconotidae Laniaruus barbarous Yellow-crowned gonolek 20. Motacillidae Motacilla flava Yellow wagtail Motacilla flava Common wagtail 21. Meropidae Merops pusillus Little bee-eater Merops orientalis Little green bee-eater 22. Musophagidae Crinifer piscator Western grey plantain-eater Crinifer piscator Plantain eater 23. Nectariniidae Cinnyris pulchellus Beautiful sunbird Hedydipna platura Pygmy sunbird 24. Ploceidae Ploceus spp Weavers Bubalornis albirostris Buffalo weaver Plcepasser Chestut-crowned superciliosus sparrow weaver Anomalospiza imberbis Cuckoo finch Quelea quelea Red-billed quelea Ploceidae Bishop Ploceus luteolus Little weaver Anaplectes rubriceps Red-headed quelea Ploceus cucullatus Village weavers Sporopipes frontalis Speckle-fronted weaver Ploceus vitellinuus Vitelline masked weaver 25. Passeridae Passer luteus Sudan golden sparrow Petronia dentate Bush petronia Passer griseus Northern grey-headed sparrow 26. Phasianidae Ptilopachus petroosus Stone partridge Francolinus Clapperton's clappertoni francolin 27. Phalacrocoracidae Phalacrocorax Long-tailed comorant africanus 28. Picidae Dendropicos goertae Grey woodpecker 29. Psittacidae Psittacula krameri Rose-ringed parakeet Poicephalus sensgalus Senegal parrot 30. Phoeniculidae Phoeniculus purpureus Green woodhoopoe 31. Pycnonotidae Pycnonotus barbatus Common bulbul 32. Recurvirostridae Himantopus himantopus Black-winged stilt 33. Sturnidae Lamprotornis pulcher Chestnut-bellied starling Lamprotornis purpureus Purple glossy starling Lamprotornis caudatus Long-tailed starling 34. Scolopacidae Actitis hypoleucos Common sandpiper Calidris minuta Little stint Philomachus pugnax Ruff Tringa glareola Wood sandpiper 35. Sylviidae Sylvia communis Common whitethroat Sylvia curruca Lesser whitethroat Hippolias polyglotta Melodious warbler Sylvietta brachyuran Northern combrec Hippolais spp Sedge wabler Acrocephalus Tawny-flanked prinia schoenobaenus Prinia subflava Warbler Sylvia spp Willow warbler 36. Threskiornithidae Plegadis falcinellus Gossy ibis Threskiornis Sacred ibis aethiopica 37. Timaliidae Turdoides plebejus Brown babblers 38. Turdidae Cercotrichas podobe Black scrub robin Myrmecocichla aethiops Northern anteater chat 39. Upupidae Upupa epops Hoopoe 40. Viduidae Vidua macroura Pin-tailed whydah Vidua orientalis Sahel paradise whydah Vidua chalybeate Village indigobird Euplectes spp Widow bird