Golden Eagle Occupancy Surveys and Monitoring Strategy in Coastal Southern California, United States

Frontiers in Ecology and Evolution

Ecology and Evolution

Peter H. Bloom¹  J. David Wiens²  Patrick S. Kolar²  Melanie C. Madden³  Jeff A. Tracey³  Robert N. Fisher³ 

[1] Bloom Research Inc., Santa Ana, CA, United States;U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR, United States;U.S. Geological Survey, Western Ecological Research Center, San Diego, CA, United States;

关键词: California birds;    detection probability;    golden eagle;    Aquila chrysaetos;    N-mixture model;    occupancy model;   

DOI  :  10.3389/fevo.2021.665792

 received in 2021-02-08, accepted in 2021-12-09,  发布年份 2022

来源: Frontiers

【 摘 要 】

Golden eagles (Aquila chrysaetos) are of increasing conservation concern in western North America. Effective conservation measures for this wide-ranging, federally protected raptor species require monitoring frameworks that accommodate strong inference on the status of breeding populations across vast landscapes. We used a broad-scale sampling design to identify relationships between landscape conditions, detection rates, and site occupancy by territorial pairs of golden eagles in coastal southern California, United States. In 2016 and 2017, we surveyed 175 territory-sized sample sites (13.9-km2 randomly selected grid cells) up to four times each year and detected a pair of eagles at least once in 22 (12.6%) sites. The probability of detecting pairs of eagles varied substantially between years and declined with increasing amounts of forest cover at survey sites, which obscured observations of eagles during ground-based surveys. After accounting for variable detection, the mean estimate of expected site occupancy by eagle pairs was 0.156 (SE = 0.081). Site-level estimates of occupancy were greatest (>0.30) at sample sites with more rugged terrain conditions, <20% human development, and lower amounts of scrubland vegetation cover. The proportion of a sample site with open grassland or forest cover was not strongly correlated with occupancy. We estimated that approximately 16% of the 5,338-km2 sampling frame was used by resident pairs of golden eagles, corresponding to a sparsely distributed population of about 60 pairs (95% CI = 19 – 151 pairs). Our study provided baseline data for future surveys of golden eagles along with a widely applicable monitoring framework for identifying spatial conservation priorities in urbanizing landscapes.

【 授权许可】

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Copyright © 2022 Wiens, Bloom, Madden, Kolar, Tracey and Fisher.