Estimating Western Scrub-Jay Density in California by Multiple-Covariate Distance Sampling

The condor

Scott P. Crosbie¹ 

关键词: abundance;    Aphelocoma californica;    density;    distance sampling;    point transect;    Western Scrub-Jay;   

DOI  :  10.1525/cond.2011.090152

学科分类：动物科学

来源: Central Ornithology Publication Office

【 摘 要 】

Abstract. Using multiple-covariate distance sampling with seasonal point transects, we surveyed for the Western Scrub-Jay (Aphelocoma californica californica group) over a substantial portion of its range in California . Our goals were to produce seasonal and habitat-specific estimates of the scrub-jay's regional density and abundance in 2008 and to demonstrate how the concurrent collection and analysis of covariate data may be useful in improving estimates of bird density. Density and abundance estimates implied a significant 38% increase over 2008, from a low of 24 jays km-2 (2.3 × 106 jays) in February to a high of 78 jays km-2 (7.5 × 106 jays) in November. Density was greatest in agricultural habitats (98 jays km-2) and least in rural habitats (38 jays km-2). Averaged over the study, abundance was greatest in agricultural habitats (2.6 × 106 jays) and least in urban habitats (3.6 ×105 jays). Inclusion of covariates such as habitat type, observer, weather, and time of day often increased the precision ...

【 授权许可】

CC BY