Population and Demographic Trends of Ferruginous Pygmy-owls in Northern Sonora 2000-2007 and Implications for Recovery in Arizona
Cactus ferruginous pygmy-owls (Glaucidium brasilianum cactorum) are of profound conservation concern in southern Arizona where populations have declined precipitously and are now thought to be extinct east of the Santa Cruz River. Augmentation and recovery of pygmy-owls in Arizona likely depends on habitat restoration and efforts to foster immigration from neighboring Sonora, Mexico where pygmy-owls are more abundant. As such, information on status and trends of populations of pygmy-owls in northern Sonora are important to assess long-term prospects for persistence in the region, to identify potential source populations of immigrants, and to answer questions that are fundamental to management and recovery. In 2000, I began monitoring population and demographic trends of pygmy- owls in northern Sonora in a large region (25,000 km2) that is immediately adjacent to and within 110 km of Arizona (Fig. 1). Over eight consecutive years, I monitored population and demographic parameters of pygmy-owls in an effort to describe the status and trends of this population. To assess environmental factors that could potentially drive these trends, I considered annual estimates of rainfall and prey abundance measured at regional scales and vegetation and land-use factors measured along transects where I monitored owls. This report summarizes the major accomplishments and findings of this program and discusses implications and potential future applications of these data. Methods used to collect and analyze data are described elsewhere (Flesch and Steidl 2006, Flesch 2007) except where noted and will be reported in greater detail in the future.