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eBook details

• Title: Distribution and Abundance of Western Burrowing Owls (Athene Cunicularia Hypugaea) in Southeastern California (Report)
• Author : Southwestern Naturalist
• Release Date : January 01, 2011
• Genre: Life Sciences,Books,Science & Nature,
• Pages : * pages
• Size : 202 KB

Description

The western burrowing owl (Athene cunicularia hypugaea) has declined in recent decades across much of its range (Wedgwood, 1978; James and Ethier, 1989; Sheffield, 1997a; Holroyd et al., 2001; Wellicome and Holroyd, 2001; DeSante et al., 2007), including California, where it is classified as a species of special concern (Gervais et al., 2008; Shuford and Gardali, 2008). Primary causes of the decline likely have included loss of grassland and agricultural habitats to urbanization (Trulio and Chromczak, 2007) and conversion of lands to inhospitable crops, such as orchards and vineyards (Gervais et al., 2008). Populations in imperial Valley and in some other areas of the state, where agricultural practices permit, thrive at much higher densities than populations in natural grasslands (DeSante et al., 2004). other suggested causes of decline include eradication of fossorial mammals (Zarn, 1974; Holroyd et al., 2001; J. V. Remsen, Jr., in litt.) and exposure to pesticides and other contaminants (Haug et al., 1993; Sheffield, 1997b; Gervais and Anthony, 2003). Each of these factors, and potentially others, may be important in California, which hosts one of the largest populations of western burrowing owls of any state or Canadian province (Barclay, 2007). Excluding the desert and Great Basin regions, DeSante et al. (2007) estimated the breeding population in California was 9,266 pairs in 1993. Although burrowing owls occupy the vast deserts of southeastern California (Garrett and Dunn, 1981), estimates of size of populations for these areas based on systematic surveys have not been published. Anecdotal information indicates that burrowing owls generally are scarce in the region, particularly in easternmost portions (Garrett and Dunn, 1981), and that a substantial concentration occurs along the Colorado River in Palo Verde Valley (Gervais et al., 2008). However, quantitative, survey-based estimates of size of populations and knowledge of distributional patterns are needed for prioritizing conservation efforts in California (Burkett and Johnson, 2007).

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