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Home range and use of habitat of western yellow-billed cuckoos on the middle Rio Grande, New Mexico.

The western yellow-billed cuckoo (Coccyzus americanus occidentalis) is a riparian obligate subspecies with declining populations in the western United States. Western populations of the cuckoo are classified as a Distinct Population Segment by the United States Fish and Wildlife Service (2001), although they are typically referred to as a distinct subspecies (S. E. McNeil et al., in litt.). The cuckoo has been proposed for listing under the United States Endangered Species Act and is listed as threatened, endangered, or sensitive by the states of California, Arizona, New Mexico, Colorado, and Utah (United States Fish and Wildlife Service, 2001).

Anticipation of a listing action has highlighted the lack of information on natural history and site-specific data that could aide in recovery of the western yellow-billed cuckoo. The spatial scale (size of home range) and vegetative mosaic (utilization of habitat) that a given species selects for breeding are measurements with biological importance, often used in concert to define requirements of habitat for a given species (Southerland and Green, 2004). The direct application of this information has obvious utility when planning recovery for a species (United States Fish and Wildlife Service, 2001; Anich et al., 2009). It is clear that western cuckoos have experienced a range-wide reduction in occupancy and number. This phenomenon has been described as catastrophic (Hughes, 1999) and drastic (Laymon and Halterman, 1987) and more mildly as substantial (M. J. Johnson et al., in litt.). Biologists largely attribute the declines to loss of habitat, with the habitat for the species limited within its historical range (Greco, 2008), and that documenting spatial use of riparian breeding range of the western yellow-billed cuckoo using empirical data is a high priority for recovery efforts.

We implemented a study of home range using radio telemetry in 2007 and 2008 to determine size of home range, maximum distance traveled, and utilization of habitat along the portion of the Rio Grande flowing through central New Mexico, locally referred to as the Middle Rio Grande. Cuckoos are cryptic and difficult to detect (Halterman, 2009), and radio tracking has proven an effective method for determining spatial requirements of the cuckoos in southwestern riparian systems (Laymon and Halterman, 1987; Halterman, 2009; S. E. McNeil et al., in litt.). The objectives of this study were to document spatial traits (e.g., size of home range, distance travelled, and utilization of habitat) of cuckoos on the Middle Rio Grande that could help conserve the species, including defining criteria for recovery for this system as well as other cuckoo breeding ranges throughout the western United States.

MATERIALS AND METHODS--The study was conducted upstream of the pool of Elephant Butte Reservoir on the Middle Rio Grande in central New Mexico (Fig. 1). We divided the study area into reaches based on the historic elevation of a full pool of Elephant Butte Reservoir during the study, and on the type of vegetation, flooding over banks, and landforms present as the level of the pool decreased. The Mainstem Reach is the historic river channel above the historic full-pool elevation from Reclamation river mile 84-62 (Reclamation river miles = 0 at Caballo Dam, New Mexico, and increase moving upstream). The riparian widths of this reach ranged from 0.4-3.2 km, and the canopy of the 2,332 ha was a mature native and exotic vegetation with sparse native and exotic understory. This reach was levied, with periodic confined flooding over banks. The Delta Reach is the historic inflow of the reservoir at full pool from river mile 62-46. The riparian widths of this reach ranged from 0.8-4 km, and the canopy of the 3,562 ha was mixed native seral stage with mixed seral stage understory of native and exotic vegetation. This reach was channelized with periodic flooding over banks. The Narrows Reach is a distinctive section of the Middle Rio Grande dominated by high cliffs that, during this study, preceded the new and lower inflow to the reservoir from river mile 46-41. The riparian widths ranged from 0.16-1.20 km, and the canopy of the 271 ha was immature native species with an understory of young, mixed native and exotic vegetation. The reach was channelized and received periodic flooding over banks with longer periods of inundation associated with fluctuation of the reservoir.

The western yellow-billed cuckoo utilizes the riparian forests found along the river, with dominant species of trees being native willow (Salix gooddingii) and cottonwood (Populus) and exotic saltcedar (primarily Tamarix chinensis, though other species of Tamarix are present). Using ground-truthing and aerial interpretation from high-resolution aerial photography (flown in 2007; color-infrared, raster resolution = 0.6 m), we identified habitat used by, or available to, cuckoos along the Middle Rio Grande and then classified the habitat as types following V. C. Hink and R. D. Ohmart (in litt.). These original classifications were simplified (D. Aiders et ah, in litt.) to create a classification system that would represent broader seral stages. For example, vegetational polygons could be comprised only of an overstory component (canopy with no understory and >4.5 m), an understory component (no canopy cover and ranging from 1.5-4.5 m), or both; while young successional stands comprised vegetation <1.5 m. The modified classification system also represents the general species of plants present (e.g., native, mixed, or exotic), consisting of species such as willow, cottonwood, saltcedar, Russian olive (Elaeagnus angustifolia), New Mexico olive (Forestiera neomexicana), and seep willow (Baccharis salicifolia). Vegetative dominance (native or exotic) was defined as >75%; mixed communities were comprised of native and exotic vegetation with no one type >75%.These data were subsequently digitized into an ArcMap polygon shapefile (Environmental Systems Research Institute, ESRI(r), Redlands, California) with distinct polygons for each type of vegetative community.

We located cuckoos via standardized presence-absence surveys conducted throughout the study area in 2007 and 2008 (D. Aiders et ah, in litt.). Locations with clusters of multiple detections of cuckoos were given priority to maximize netting efforts within the river reaches, and specific locations of capture were chosen based on topography, vegetative cover, and availability of natural netting lanes. Cuckoos were target-netted using call-playback and arrays of stacked mist nets based on the methodology of Halterman (2009). We used mist nets with standard 60-nnn mesh, in lengths of 6, 9, or 12 m, and 2.6-m high. Typically, two nets of the same length were sewn together and stacked (e.g., two 6-m nets were sewn together, one on top of the other, to form an eight-shelf net that was 6-m long and 5.2m high). Captured cuckoos were immediately banded, weighed, measured (length and depth of bill; tarsus length; tail length, rectrix insertion to tip; wing chord; and keel fat), and a blood sample (20-40 [micro]l, microhematocrit tube) was collected and transferred to a PermaCode card (Avian Biotech International, Tallahassee, Florida) for sexing by analysis of DNA. We used a 1.8-g BD-2 radio transmitter (Holohil Systems Ltd., Ontario, Canada) sutured between the central rectrices (see Halterman, 2009); weight of a transmitter was ca. 2.8% of the average body mass of the captured cuckoos. Transmitters had a range of ca. 0.5 km and a nominal battery life of 11 weeks. Automatic scanning receivers with computer interfaces (model R2100, Advanced Telemetry Systems, Isanti, Minnesota) were coupled with three-element Yagi antennas to receive signals from radio-instrumented cuckoos. All captured cuckoos were assumed to be breeding adults based upon the presence of a brood patch, recorded weights, and morphological characteristics provided in Hughes (1999) and Pyle (1997), and occupation during the known period of residence for breeding birds. The exception was bird 3 (2007) which was determined to be a second-year male based on weight and the presence of an eye ring.

[FIGURE 1 OMITTED]

We tracked telemetered cuckoos from upland areas ca. 5-20 m above the riparian plane in proximity to locations of capture in each reach of the river from 2 July-6 August 2007 and 19 June-20 August 2008. When a telemetered cuckoo was located, we attempted to track it continuously throughout the day (ca. 2 days of 8-10 h each/week in 2007 and 1 day/week in 2008) using the tracking methodology of Sechrist and Ahlers (2003). Two technicians would simultaneously collect information on location of a targeted cuckoo using handheld radios to coordinate timing of acquisition and bearing. Detected signals were first located via compass bearing and a Universal Transverse Mercator (UTM) coordinate recorded from a Global-Positioning-System unit at the location of each technician.

These two bearings and locations were input into a spreadsheet model on-site upon acquisition of the signal (Sechrist and Ahlers, 2003; also Newmark et al., 2010; S. E. McNeil et al., in litt.). The spreadsheet model determined if a signal location could be calculated based on a computed intersection of bearings or whether another position fix was required. Sechrist and Ahlers (2003) conducted error trials using this methodology while radio-tracking brown-headed cowbirds (Molothrus ater) on the Middle Rio Grande. Technicians were consistently able to locate actual transmitters within 200 m. During this study, we determined that positional error was likely lower. This is based on triangulated positions (n = 2) collected for an individual cuckoo on the same day that its cast transmitter was found and the position of the transmitter could be confirmed with a UTM position. In these instances, it was determined that telemetric data were accurate to within an average of 63 m. Further, Morath (2011) performed much more rigorous estimates of error using this methodology while researching movement and vocalization response of western yellow-billed cuckoo within the study area. Ad hoc analysis was performed by finding the mean difference in the 24 points recorded from a stationary transmitter. It was found that the range of movement-error over distance during two trials was 21.9 and 30.1 m.

At least four valid location-points were collected per hour (Sechrist and Ahlers, 2003; Newmark et al., 2010). Overall, we attempted to collect a minimum of 100 points/telemetered cuckoo over the course of its period of residence on the Middle Rio Grande (ca. 15 June-15 August; see Hunter et al., 1985 for a range of detections at different locations in New Mexico). For cuckoos that were in areas difficult to access (e.g., far from roads), we tried to determine general locations to begin telemetry by aircraft or on foot. The effort was not randomized; the overall size and habitat of the study area precluded this. Instead, as the period of residence progressed towards the estimated end of the breeding season, more effort was made to locate and track cuckoos that had been difficult to located or had few valid locations.

Telemetric data were analyzed to provide estimates of home range, daily and seasonal maximum distance traveled, and utilization of habitat for individual cuckoos in both years. We calculated home ranges using the Animal Movements extension (P. N. Hooge and B. Eichenlaub, 1997, http://alaska.usgs.gov/ science/biology/spatial/gistools/animal_mvmt.php)

in Arc-View (ESRI(r), Redlands, California). The 100%-minimumconvex-polygon (MCP; Mohr, 1947; Shekel, 1954; Jennrich and Turner, 1969) and the fixed-kernel-home-range estimators (KHR; Worton, 1989) were used to estimate sizes of home range. The KHR output for each individual provided calculations of home ranges of cuckoos for 50%-probability and 95%probability polygons, with smoothing determined by ad hoc least-squares cross-validation (Silverman, 1986). The MCP estimates of home range were based on the ability of the ArcView Spatial Analyst program to completely enclose all location points for each individual cuckoo by connecting the outermost locations and, thus, creating a convex-shaped polygon. The daily maximum distance was calculated based on the greatest straight-line distance between locations collected in a given day of tracking. A day of tracking was considered a minimum of three valid locations per day with at least one location collected per hour. Maximum seasonal distance was calculated as the greatest straight-line distance that could be calculated from two points collected over the course of all days tracked, e.g., the greatest distance across a MCP.

Size (hectares) of home range and movement distance (meters) were compared for differences between years using a nonparametric Mann-Whitney Rank Sum Test (Zar, 1984). If no difference was found, the 2 years of data were pooled (because of the small annual sample sizes) to assess differences in size of home range or maximum seasonal distance travelled as a function of sex or river-reach using the nonparametric Mann-Whitney Rank Sum Test.

Utilization of habitat by individual cuckoos was calculated based on the 50 and 95% KHR probabilities. To determine the proportion of each vegetative type associated with the core and total home range of a cuckoo, we clipped the vegetative polygon for 50 and 95% KHR home ranges using the Geoprocessing Wizard within ArcMap (ESRI(r), Redlands, California). A chi-square test was used to determine whether the observed proportional areas of vegetative type used in the 50% KHR were similar to the expected proportional areas of vegetative type used in the 95% KHR (e.g., availability-utilization analysis, see Neu et al., 1974). All data from the 95% KHR calculations for both years were pooled to yield total areas of each vegetative type used.

The number of nonoverlapping home ranges the study area is capable of supporting was estimated using the total riparian area within each reach divided by the average size of home range (95% KHR) of birds associated with the reach. These data were compiled periodically because of the drawdown of Elephant Butte Reservoir, and recolonization by native or exotic plants led to an increase in habitat in formerly inundated areas (D. Aiders et al., in litt.).

RESULTS--We captured five cuckoos (three males, two females) in 2007 and eight cuckoos (three males, three females, and two adults of unknown sex) in 2008 in three river-reaches of the Middle Rio Grande, New Mexico. Three of five cuckoos captured in 2007 provided location data to calculate estimates of movement and home range, having been tracked an average of 10 days ([+ or -]3 SI), range of 8-13) to obtain a mean of 132 locations/bird ([+ or -]10 SI). range of 123-143). In 2008, seven of eight cuckoos captured provided data on location and were tracked an average of 6 days ([+ or -]3 SI), range of 1-10) to obtain a mean of 77 locations/bird ([+ or -]36 SI), range of 15-114; Table 1). Bird 4 (2008) was located late in the period of residence and was only tracked for 1 day prior to loss of signal; thus, this bird was excluded from the majority of the analyses of movement and home range.

Male and female cuckoos tracked in 2007 had daily movements averaging 579 m ([+ or -]361 SI), range of 351-995) and seasonal movements averaging 709 m ([+ or -]382 SI). range of 365-1,120). Cuckoos tracked in 2008 had daily movements averaging 876 m ([+ or -]528 SI), range of 204-1.716) and seasonal movements (n = 6, bird 4 excluded) averaging 2,045 m ([+ or -]1,043 SI), range of 917-3,143; Table 1, Fig. 2). The average daily distance traveled for both years combined was 786 m ([+ or -]485 SI), range of 204-1.716), with an average seasonal movement distance of 1,599 m ([+ or -]1,078 SI), range of 365-3,143). There was no significant difference in daily or maximum seasonal distance traveled between years (U = 14, P = 0.517 for daily; U = 16, I' 0.095 for seasonal); therefore, data for both years were pooled for subsequent testing. We failed to detect a significant difference in daily or maximum seasonal distance traveled between sexes (unknown sex excluded, U = 9, P = 0.786 for daily, U = 9, P = 0.786 for seasonal) or between reaches (Narrows versus Delta U = 10, P = 0.571 for daily, U = 10, P = 0.571 for seasonal).

Cuckoos tracked in 2007 had a mean MCP of 27 ha ([+ or -]27.9 SD, range of 5-58), and mean 50 and 95% KHR probabilities of 9 and 27 ha ([+ or -]12.8 SD, range of 0.5-6.0 for 50% KHR and [+ or -]30.8 SI), range of 4-62 for 95% KHR). Cuckoos tracked in 2008 (n = 6, bird 4 excluded) exhibited a mean MCP of 123 ha ([+ or -]95.2 SI), range of 21.6-282.0), and mean 50 and 95% KHR probabilities of 10 and 80 ha ([+ or -]8.5 SD, range of 3.2-24.2 for 50% KHR and [+ or -]62.8 SD, range of 18.1-157.2 for 95% KHR; Table 1, Fig. 2). Cuckoos tracked in 2007 and 2008 combined had an average MCP size of 91 ha (bird 4 excluded; [+ or -]90.4 SI). range of 5.0-282.0) and overall mean 50 and 95% KHR size of 10 and 62 ha, respectively (bird 4 excluded; [+ or -]9.3 SI), range of 0.5-24.2 for 50% KHR and [+ or -]58.3 SD, range of 4.0-157.2 for 95% KHR; Table 1). There was no significant difference in MCP or the 95% KHR mean size of home range between years (U 16, I' 0.095 for MCP; U = 15, P = 0.167 for 95% KHR); therefore, data for both years were pooled for subsequent testing. There was no statistically significant difference in either the MCP or the 95% KHR mean size of home range by sex (unknown sex excluded, U = 4, P = 0.857 for MCP; U = 5, P = 1.000 for 95% KHR), although our small sample size suggest low power to detect a difference if it exists. Schoener's ratio (Schoener, 1981) was applied to the data used to generate the estimates of home range to quantify the degree of autocorrelation; all home ranges presented were positively autocorrelated.

The home ranges calculated for 2007 and 2008 were associated with different reaches of the Middle Rio Grande. The five cuckoos captured in 2007 were distributed from the Mainstem of the Middle Rio Grande to the Narrows; however, the three birds that provided information were associated with the Delta (n = 1) and the Narrows reaches (n = 2). The distribution was similar in 2008, but the majority of data for home range was associated with the Delta reach (five of eight birds tracked). The Narrows and Mainstem reaches provided useable data for one cuckoo each. Using data for both years, we did not detect a statistically significant difference in size of home range for either the MCP or the 95% KHR when comparing the Delta and Narrows (U = 10, P = 0.571 for MCP; U = 11, P = 0.393 for 95% KHR). Two cuckoos were excluded from the analysis; cuckoo 2 (2008) was located in the Mainstem reach and cuckoo 4 (2008) was tracked for only 1 day.

[FIGURE 2 OMITTED]

The number of nonoverlapping home ranges of cuckoos that the study area could support was estimated by reach using the 95% KHR and area of each reach. We used the reach-specific average estimate of 95% KHR size as well as the average estimates of 95% KHR over the entire study site to estimate the number of home ranges that could be supported in the riparian zones for each reach. Overall, and assuming an even distribution of resources, we estimate the carrying capacity of our study area to be 82-99 home ranges (Table 2).

We estimated the importance of different vegetative types occurring within the core home range (50% KHR) versus overall home range (95% KHR) using an availability-utilization analysis (Neu et al., 1974) to compare the proportional differences for all nine cuckoos (2007 and 2008 combined). This method allowed evaluation of preference or avoidance of specific habitat and was used in conjunction with a chi-square analysis (Neu et al., 1974). There was no evidence that the birds use vegetative types in ratios different from what is available based on a chi-square test ([chi square] = 0.20, df = 17, P = 1.00). However, based on used minus available vegetation (Table 3), we compiled a qualitative assessment of possible preference and possible avoidance for the 50% KHR (Fig. 3).

DISCUSSION--We found that movement and size of home range of western yellow-billed cuckoos along the Middle Rio Grande in New Mexico varied widely among individuals but generally were larger than those estimated from other studies in California (MCP = 17.0; Laymon and Halterman, 1987) and Arizona (95% MCP = 51.1 [+ or -] 62.4, 95% KHR = 38.6 [+ or -] 42.2, 50% KHR = 7.5 [+ or -] 10.3, Halterman, 2009; 100% MCP = 27.6 [+ or -] 15.0 and 42.9 [+ or -] 15.0, 95% KHR = 21.6 [+ or -] 8.8 and 21.7 [+ or -] 10.4, 50% KHR = 3.8 [+ or -] 1.6 and 4.3 [+ or -] 2.3, S. E. McNeil et al., in litt.). The small sample sizes in other studies (e.g., Laymon and Halterman, 1987) and the widely variable characteristics of sites among studies (e.g., small riparian restoration sites found in S. E. McNeil et al., in litt., versus large tracts of mixed riparian in Halterman, 2009) makes broad-scale comparisons of the size of home range of cuckoos among studies difficult. Site-specific variation is likely a result of characteristics unique to each location (e.g., types and quality of habitat, configuration of patch), and flexible home ranges with overlapping territories in this weakly territorial species (Hughes, 1999; Halterman, 2009). For the purposes of our study, we make two large assumptions: 1) that home ranges or territories of cuckoos do not overlap; 2) that no other factors such as hydrology, increasing or decreasing availability of habitat, or prey base affect these numbers. We acknowledge these assumptions frame our estimates of home range as rigid delineations and are, therefore, conservative; however, when estimate of territory after 2008 were modified to allow for overlap (D. Aiders et al., in litt.), the increase in overall territories was small (Table 2).

Relatively few species of riparian birds have been studied to quantify home ranges, but a study of another obligate riparian species, the southwestern willow flycatcher (Empidonax traillii extimus) in Arizona found home ranges substantially smaller (mean 95% kernel estimate = 0.23 ha for breeding individuals; S. N. Cardinal and E. H. Paxton, in litt., (http://sbsc.wr.usgs.gov/cprs/research/ projects/swwf/Reports/telemetry2004report.pdf), suggesting very different spatial requirements for these two species that often co-exist in the same riparian woodlands. While our work contributes to overall understanding of the range of variation in spatial requirements of the cuckoo, and more generally to species of riparian obligate birds, clearly more research is needed to understand the factors driving variation.

[FIGURE 3 OMITTED]

We found no statistical support for preferences in habitat, although some habitats were used above or below availability. Yellow-billed cuckoos in the western United States have been documented breeding in a wide range of habitats across their range, from pure stands of exotic tamarisk on the Pecos River (J. Sechrist, pens, obset; populations on the Pecos River considered part of the eastern subspecies C. a. americanus) to mesquite bosques (Halterman, 2009) in Arizona to native cottonwood gallery forests on the Sacramento River in California (Laymon and Halterman, 1987; Greco, 2008). Nonetheless, cuckoos occur in a very small fraction of existing riparian woodlands, despite a wide range of types and structure of vegetation occurring at the landscape level, suggesting there are narrow constraints in habitat. The use of a 50% KHR to represent a core-area for migratory landbirds is widely supported in the literature (e.g., Vega Rivera et al., 2003; Newmark et al., 2010). Thus, our analysis of preference of habitat (Fig. 3) is a good starting point for delineating critical habitat for this species on the Middle Rio Grande and to develop hypotheses for further research. Breeding cuckoos are thought to be weakly territorial (Hughes, 1999); therefore, these data likely represent selection of habitat based on availability of resources. Our findings indicate that, apparently, preferred habitat for cuckoos on the Middle Rio Grande includes an overstory of native canopy with mixed-seral-stage understory comprised of native and exotic vegetation. We acknowledge that this information is still qualitative and that it is bounded by the limitations of small sample sizes coupled with telemetric error and broad-scale categories of riparian vegetation. However, we know of no other study for this species that has derived preference data from estimates of the home range of cuckoos, although other studies inferred preference of habitat based primarily on characteristics of patches (e.g., dominant riparian plant, patch size of habitat, indices of habitat-suitability, or occupancy; Hunter et al., 1985; Laymon and Halterman, 1987; Greco, 2008; M. J. Johnson et al., in litt.; S. E. McNeil et al., in litt.).

The Middle Rio Grande hosts the largest population of cuckoos in New Mexico and what is believed to be one of the largest remnant populations of the western yellow-billed cuckoo in the southwestern United States (D. Aiders et al., in litt.). In comparison, one of the sites with the highest density (based on detections during surveys) along a 644-km reach of the Lower Colorado River, the Bill Williams River National Wildlife Refuge, was estimated to support a maximum of 31 pairs of cuckoos (S. E. McNeil et al., in litt.). It is notable that territory is not defined within the widely accepted protocol for surveys developed by the Yellow-billed Cuckoo Working Group (M. M. Halterman et al., in litt.), but, for the purpose of surveys of populations, we define a territory as a dumping of detections over at least three surveys, representing a pair, suspected pair, or unpaired male, and our techniques for delineating territories varied from 2006-2008 (V. Johanson et al., in litt.) and 2009-2011 (D. Ahlers et al., in litt.).

Surveys of populations of yellow-billed cuckoos on the Middle Rio Grande indicate increasing numbers of territories of cuckoos, from 44 in 2006 to 83 in 2009 (D. Ahlers et al., in litt.). Although there is limited information regarding the mechanisms associated with this increase, we speculate that the maintenance of continuous, unfragmented riparian corridor on the Middle Rio Grande and the rapid, continual revegetation of formerly inundated areas associated with lowering water levels of Elephant Butte Reservoir are responsible. Our study area encompassed a 69-km unbroken reach of the Middle Rio Grande with little or no anthropogenic influences (other than seasonal grazing by livestock), and ca. 3,800 ha of rapidly maturing, mixed seral stage, native and exotic vegetation has become re-established on the Delta and Narrows reaches since the mid-1990s. Our estimate of 82-99 home ranges of cuckoos which can potentially be supported within the Middle Rio Grande riparian zone is in agreement with the number of territories estimated from annual surveys of cuckoos in 2009 (Table 2) and may indicate the study area is approaching carrying capacity for this species. If the species is listed as threatened or endangered under the Endangered Species Act, resource managers on the Middle Rio Grande will need to reasonably approximate goals for recovery to better assess potential impacts to the species as well as meet or exceed targets for recovery.

Clearly, further investigations are merited, and we suggest that future studies of home range and utilization of habitat for this species incorporate larger sample sizes with greater duration of tracking over multiple years. Also, factors driving patterns of home range, such as breeding status, should be an integral part of such studies. Radio telemetry is still the most effective means of collecting data for this cryptic species, but other methods such as tracking large-scale movement via light-level geolocators (Sechrist et al., 2012) can be important for understanding requirements for habitat at the landscape level.

We thank the Albuquerque Area Office and the Research and Development Program of the United States Bureau of Reclamation for funding associated with this project. We appreciate the time and effort our seasonal technicians spent assisting with collection of data and thank C. Fields for assistance with Interlibrary Loan Materials. Y. E. Porras Mendoza provided the Spanish translation of the abstract. Also, we would like to recognize D. Carstensen and S. Kennedy for managing fieldwork on the Middle Rio Grande during this study. The use of product trade names in this paper does not constitute product endorsement by the United States government.

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Submitted 1 February 2012. Accepted 12 December 2013.

Associate Editor was Karen Francl.

JUDDSON SECHRIST, * DARRELL D. AHLERS, KATHERINE POTAK ZEHFUSS, ROBERT H. DOSTER, EBEN H. PAXTON, AND VICKY M. RYAN

United States Bureau of Reclamation, Denver Technical Service Center, Denver, CO 80225 (JDS, DDA) North Wind Inc., Denver Technical Service Center, Denver, CO 80225 (KPZ)

United States Fish and Wildlife Service, Pacific Southiuest Region Migratory Bird Program, 2800 Cottage Way, Sacramento, CA 95825 (RHD)

United States Geological Survey, Pacific Island Ecosystems Research Center, Hawaii National Park, HI96718 (EHP)

United States Bureau of Reclamation, Albuquerque Area Office, Albuquerque, NM 87102 (VMR)

Present address of KPZ: 5 Carissa Circle, Littleton, CO 80127

Correspondent: jsechrist@usbr.gov
Table 1--Maximum daily and seasonal movements and estimates
of home range (MCP = 100%-minimum-convex-polygon; KHR =
fixed-kemel-home-range) of radio-marked yellow-billed cuckoos
(Coccyzus american us occidentalis) along three reaches (N =
Narrows, D = Delta, M = Mainstem) of the Middle Rio Grande,
New Mexico, in 2007 and 2008.

Year and                 Sex        Days     Number of
bird (reach)                       tracked   locations

2007

  1 (N)              Male             8         123
  2 (N)              Female          13         143
  3 (D)              Male             8         129
  Mean [+ or -] SD

2008

  2 (M)              Female          10         114
  3 (D)              Male             6         105
  4 (a) (D)          Female           1          15
  5 (D)              Male             6          60
  6 (D)              Male             7          51
  7 (N)              Unknown (b)      8          88
  8 (D)              Unknown (b)      5         107
  Mean [+ or -] SD

Years combined

Year and                 Maximum              Maximum
bird (reach)              daily               seasonal
                         distance             distance
                           (m)                  (m)

2007

  1 (N)                    351                  365
  2 (N)                    392                  642
  3 (D)                    995                 1,120
  Mean [+ or -] SD   579 [+ or -] 361     709 [+ or -] 382

2008

  2 (M)                   1,716                3,143
  3 (D)                    487                  917
  4 (a) (D)                204                   --
  5 (D)                    818                 1,386
  6 (D)                    551                 2,790
  7 (N)                   1,365                3,007
  8 (D)                    989                 1,024
  Mean [+ or -] SD   876 [+ or -] 528   2,045 [+ or -] 1,043

Years combined       786 [+ or -] 485   1,599 [+ or -] 1,078

Year and             Estimator of home range (ha)
bird (reach)
                               MCP                  95% KHR

2007

  1 (N)                        5.0                    4.0
  2 (N)                       16.5                    15.0
  3 (D)              58.0 27.0 [+ or -] 27.9        62.0 (c)
  Mean [+ or -] SD                             27.0 [+ or -] 30.8

2008

  2 (M)                       282.0                  152.6
  3 (D)                       21.6                    18.1
  4 (a) (D)                    --                      --
  5 (D)                       82.0                    44.6
  6 (D)                       127.1                157.2 (c)
  7 (N)                       173.9                   84.5
  8 (D)                       48.9                    22.0
  Mean [+ or -] SD     123.0 [+ or -] 95.2     80.0 [+ or -] 62.8

Years combined         91.0 [+ or -] 90.4      62.0 [+ or -] 58.3

Year and               Estimator of
bird (reach)          home range (ha)

                          50% KHR

2007

  1 (N)                     0.5
  2 (N)                     3.5
  3 (D)                     6.0
  Mean [+ or -] SD   9.0 [+ or -] 12.8

2008

  2 (M)                    15.4
  3 (D)                     2.8
  4 (a) (D)                 --
  5 (D)                     4.4
  6 (D)                    24.2
  7 (N)                    11.0
  8 (D)                     3.2
  Mean [+ or -] SD   10.0 [+ or -] 8.5

Years combined       10.0 [+ or -] 9.3

(a) Tracked for 1 day.

(b) Sex could not be determined from genetic tests.

(c) The 95% KHR exceeds the MCP estimate; the calculated
utilization distribution for the KHR is greater than the
area enclosed by the MCP.

TABLE 2--Estimated carrying capacity of the western yellow-billed
cuckoo (Coccyzus americanus occidentalis) along three reaches of
the Middle Rio Grande, central New Mexico, 2007-2009.

                             Reach-specific
                                estimate

Reach      Available   n    95%      No. of       Overall
            habitat         KHR    territories   study-area
             (ha)          (ha)                   estimate
                                                  (95% KHR
                                                  = 62 ha)

Mainstem   2,332 (a)   1   152.6       15            38
Delta      3,562       5    60.8       59            57
Narrows      271       3    34.5        8             4
Combined   6,165                       82            99

Reach          Territory
               survey (b)

           2007   2008   2009

Mainstem    28     29     25
Delta       34     38     40
Narrows      7     10     18
Combined    69     77     83

(a) Only for active floodplain.

(b) Data for 2007 and 2008 incorporated estimates of nonoverlapping
territory. Data or 2009 incorporated estimates of overlapping
territory.

Table 3--Availability-utilization analysis of vegetative types found
within home ranges (kemel-home-range estimates, KHR) of western
yellow-billed cuckoo (Coccyzus americanus occidentalis) on the
Middle Rio Grande, central New Mexico.

Vegetative type                     Area (a) used (ha)

                                    95% KHR   50% KHR

Native canopy-mixed understory        39.1      9.2
Native understory                     29.1      6.9
Exotic young successional stands      37.2      6.5
Native canopy-native understory       22.0      4.6
Mixed understory                      34.2      5.7
Surface water                         26.0      3.7
Exotic understory                     90.2     11.6
Exotic canopy-exotic understory        0.3      0.0
Exotic canopy-mixed understory         1.4      0.0
Native canopy-marsh understory         4.2      0.1
Native canopy                         32.6      3.7
Mixed young successional stands        5.1      0.0
Marsh                                 28.1      2.8
Road                                   8.3      0.3
Native young successional stands       8.2      0.0
Open area                             59.9      5.3
Native canopy-exotic understory       51.4      3.7
Upland vegetation                     83.3      7.2
Total area                           560.6     71.3

Vegetative type                     Proportional area (%)

                                    Available     Used      Used minus
                                    (95% KHR)   (50% KHR)   available

Native canopy-mixed understory         7.0        12.8          5.9
Native understory                      5.2         9.6          4.4
Exotic young successional stands       6.5         9.2          2.7
Native canopy-native understory        3.9         6.4          2.4
Mixed understory                       6.1         8.0          1.9
Surface water                          4.6         5.2          0.5
Exotic understory                     16.1        16.2          0.1
Exotic canopy-exotic understory        0.1         0.0         -0.1
Exotic canopy-mixed understory         0.3         0.0         -0.3
Native canopy-marsh understory         0.7         0.1         -0.6
Native canopy                          5.8         5.2         -0.7
Mixed young successional stands        0.9         0.0         -0.9
Marsh                                  5.0         4.0         -1.0
Road                                   1.5         0.4          1.1
Native young successional stands       1.5         0.0         -1.5
Open area                             10.7         7.4         -3.3
Native canopy-exotic understory        9.2         5.2         -4.0
Upland vegetation                     14.9        10.1         -4.6
Total area

(a) Represents the total of a given vegetative type within the summed
area of all estimates of home range (n = 9) given for cuckoos in this
study.
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Author:Sechrist, Juddson; Ahlers, Darrell D.; Zehfuss, Katherine Potak; Doster, Robert H.; Paxton, Eben H.;
Publication:Southwestern Naturalist
Article Type:Report
Geographic Code:1USA
Date:Dec 1, 2013
Words:6299
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