Nest-site Selection by Cactus Ferruginous Pygmy-owls in northern Sonora Mexico.

Cactus ferruginous pygmy-owls (Glaucidium brasilianum cactorum, hereafter pygmy-owls) are the northernmost subspecies of ferruginous pygmy-owls (van Rossem 1937, Johnsgard 1988). Although once locally common in lowland central and southern Arizona (Bendire 1888, Fisher 1893, Breninger 1898, Gilman 1909, Bent 1938) pygmy-owls have been extirpated throughout much of their former range. In 1997 the United States Fish and Wildlife Service (USFWS) listed the population of pygmy-owls in Arizona as endangered (USFWS 1997). Although descriptions of areas used by pygmy-owls are essential for recovery and management efforts, research in Arizona has been limited, in part, because the scarcity of pygmy-owls has precluded detailed study.

In northern Sonora, Mexico, current information now indicates that pygmy-owls are locally common in desertscrub and semidesert grasslands within 100 km of the U.S. border (Flesch and Steidl 2000). In 2001, we located 53 pygmy-owl nests in the border region, many within 30 km of the U.S. Studying pygmy-owls in neighboring Sonora can provide information for management of U.S. populations. Our objectives are to describe the environment at and around pygmy-owl nests and to compare them to areas selected randomly within home ranges. Although preliminary, this information provides insight into the components necessary for an area to function as habitat for pygmy-owls.