Much of the concern for burrowing owls in western North America arises from their documented and suspected changes in distribution and abundance, as well as alterations of its environment, such as reductions of burrowing mammals and intensive pesticide use. These issues were recently documented in the U. S. Fish and Wildlife Service's Status Assessment and Conservation Plan. Many of these concerns are relevant in California, where large resident (breeding) and non-resident (wintering) populations exist. To better understand burrowing owl population dynamics in different habitat types, we established four intensive study areas in California in the key habitats burrowing owls occupy.
We selected four habitats in which to locate demographic study sites: (1) the urban environment, (2) intensive agriculture areas that surround small habitat patches, (3) agriculture areas in which owls nest primarily along irrigation ditches and canals, and (4) large grasslands that reflect the best examples of the native open grassland habitat and landscape typical of burrowing owls in California. This study applies both an observational and experimental approach in answering questions that relate to factors affecting the dynamics of burrowing owl populations.
Our primary objective is to understand factors affecting survivorship and productivity. We are using recent advances in mark-recapture methods to estimate survival rates and to evaluate and rank models that include various environmental and biological factors that are potentially responsible for differences among individuals and study sites. Marking individuals also allows us to estimate movement rates of young and adults, as well as to track the productivity of individual female owls.
We are also exploring the importance of additional factors, such as individual animal characteristics, pesticide exposure, diet, and microhabitat conditions, that may affect demographic parameters. These questions are the subject of on-going graduate student projects and were recently summarized in the U.S. Fish and Wildlife Service's Status Assessment and Conservation Plan.
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Former Graduate Students:
Daniel Catlin, M.S. Candidate
Within- and Between-Season Breeding Dispersal of Burrowing Owls in Grassland and Agricultural Environments