PS 87-259
Evaluating the success of the western burrowing owl in a suburban desert landscape
Burrowing owl (Athene cunicularia) populations are declining across western North America and owls are labeled as species of conservation concern in most western states. In Lake Havasu City, Arizona, owls are commonly observed in nontraditional habitats- desert washes (arroyos) in very developed, suburban locations. Suburban wash habitats may offer benefits such as a larger and more diverse prey base (due to additional and varied vegetation), perch sites, and existing burrows. However, suburban owl populations are susceptible to disturbance from human activities and vulnerable to predation by domestic dogs, cats, and coyotes, which use in-town washes as travel corridors. We began examining habitat preferences and reproductive success of burrowing owls in Lake Havasu in August, 2013. Forty-six active burrows were identified at that time using playback calls and by inspecting burrows of appropriate sizes for signs of owl activity. Habitat characteristics were recorded initially (including: burrow characteristics, wash slope and substrate, percent and type of vegetation, perch availability and proximity to human activity) and burrows were checked monthly thereafter for activity. Owl prey availability was determined by pitfall traps (arthropods), small mammal trapping and pellet analysis. Predator presence, mated pairs and chicks fledged were confirmed by use of remote cameras.
Results/Conclusions
Our study area is on the line between year round resident populations in southern Arizona and migratory owl population to the north. Preliminary results indicate that 30% of our sampled population is migratory. Pocket mice (Chaetodipus penicillatus) and Tenebrionid beetles are owls’ preferred prey and are very abundant in our suburban habitat. Eighty-three percent of washes hosting owls also host coyotes. Twenty-eight individual active burrows have been monitored since the beginning of this breeding season (Feb. 2014) and eight of these have experienced mortalities due to: coyotes (2), illness induced starvation (1) and suspected consumption of poisoned prey (5). Sixteen of the remaining burrows host mated pairs which are currently incubating eggs or caring for chicks. Habitat (burrow and site characteristics), presence of predators, human activity and prey availability will all be considered as possible predictors of nest success. To date, there have been no other similar studies of this species in suburban locations of the southwest and the burrowing owl population in western Arizona has never been studied. Our future research over the next two nesting seasons will provide baseline data on the local population as well as help biologists and managers understand the owls’ suburban habitat preferences.