Comparative demography of Burrowing Owls in urban and agricultural landscapes in southern Arizona

Despite perceived population declines in many portions of their range, burrowing owls are fairly common in urban areas throughout the western U.S. Burrowing owls are limited in some areas by available nest sites and urban areas often have natural and artificial cavities within which burrowing owls can nest. Strategies for limiting the impact of Tucson-area urban sprawl could include appropriate measures to maintain or enhance burrowing owl populations. However, certain urban environments may act as ecological traps. For example, some urban areas may attract breeding burrowing owls due to availability of nesting burrows and/or high food abundance, but may cause high mortality due to vehicle collisions, high nest predation by domestic cats, or may have other demographic consequences. Burrowing owls routinely nest in 3 distinct areas in the Greater Tucson Metropolitan area. Owls nest in round-tailed ground squirrel (Spermophilus tereticaudus) burrows on Davis-Monthan Air Force Base (DMAFB), within crevices along the banks of the Santa Cruz River that runs through the city, and on the edges of agricultural fields north of Tucson. Each of these three environments pose very different potential problems for burrowing owls. Hence, we are comparing reproductive success (e.g., nesting success, number of fledglings per nesting attempt), territory fidelity, and natal recruitment between burrowing owls nesting in these 3 different environments in the Tucson area (round-tailed ground squirrel burrows in urban areas of central Tucson, potholes along the banks of the Santa Cruz River, and under irrigation troughs within agricultural areas). This project will locate nesting burrowing owls in the Tucson area and help determine the demographic viability of urban burrowing owl populations in Tucson (e.g., whether they are self-sustaining populations or dependent on immigration from non-urban populations). We will compare our estimates of demographic parameters of burrowing owls in Tucson with populations in natural areas and other urban environments throughout the western U.S. By individually marking owls, we will also determine the proportion of Tucson burrowing owls that are year-round residents, winter migrants, and breeders.