Assessment of golden eagles in the southern Great Plains and Trans Pecos Regions
Mitchell, Natasia R.
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Golden eagles (Aquila chrysaetos) are reclusive in nature, occur at low densities, and can travel great distances, making them difficult to study. To date, there have been no studies focusing on winter density and distribution, juvenile dispersal patterns, habitat use by wintering and juvenile eagles, juvenile survival rates, and home range of juvenile golden eagles in the Southern Great Plains and Trans Pecos regions. I conducted golden eagle surveys along 51 road survey transects in the Southern Great Plains of eastern New Mexico, and the panhandles of Texas and Oklahoma during two winters. My goal was to determine land cover associations of wintering golden eagles in the region to assess potential risk from energy development, as well as the estimated density of golden eagles in the area. I also attached Platform Terminal Transmitters (PTTs) to 21 golden eagle nestlings in the Southern Great Plains region of New Mexico, Oklahoma, and Texas and the Trans Pecos region of Texas in 2015 and 2016. I used ArcMap 10.3 to analyze the habitat use of wintering and juvenile golden eagles in the study areas, analyze juvenile dispersal and movement patterns, and estimate juvenile home range. I used Program Distance 6.2 to estimate effective strip width of winter surveys, calculate a detection probability, and estimate population density during the winter surveys. I used Program MARK to analyze survival rates of juvenile golden eagles within their first post-fledging year. I found that golden eagles were detected in the shrubland and grassland cover types at greater proportion than what was available, and in the agricultural and developed land cover types less than what was available. During the December and January surveys in 2014-2015 and 2015-2016, the estimated winter density of the golden eagle population in the study area was 0.2/100km2. Survival rates were 0.6 for the first year for the 2015 cohort, 0.8 for the 2015 cohort from time of fledging until 31 December 2015, and 0.72 for the 2016 cohort from time of fledging until 31 December 2016. The mean 95% kernel home range estimates for the 2015 cohort from time of fledging to 31 December of 2015 was 12,363km2. The mean 95% kernel home range estimates for the 2016 cohort from time of fledging to 31 December of 2016 was 3,070km2.