Nest-site selection by Cooper's hawks in an urban environment

Loss of nesting habitat due to urbanization and development has been identified as a primary threat to Cooper's hawks (Accipiter cooperii), but this species can successfully nest in some urbanized areas. Hence, understanding the features of urban areas that promote occupancy by Cooper's hawks may become important in managing for the species. We measured nest tree, site, slid area features at 49 Cooper's hawk nests representing 33 breeding pairs in Tucson, Arizona between 1993 and 1996. Introduced eucalyptus (Eucalyptus spp.; 70.8%), aleppo pine (Pinus halepensis; 25.0%), and native cottonwood trees (Populus fremontii; 4.2%) were used as nest trees to a greater extent than expected based on their availability (P < 0.001). Urban nest trees were taller and of greater diameter than random trees. Nest sites (0.08 ha) were characterized by greater basal area, canopy cover, and number of trees >10 m tall when compared to random sites. Most nest trees were located in the yards of single-family residences (48.3%) and in high-use recreational areas (28.3%). Dominant land-use types in nest areas were high-density residential areas (65.9%) and high-use recreational areas (22.7%). Levels of human disturbance at nest sites did not appear to influence nest-site selection. Density of Cooper's hawks nests in Tucson was higher thrill in exurban areas and probably was associated with the large trees, water, and abundance of prey in the city. Maintaining nest sites for Cooper's hawks in Tucson will require maintaining groves of large trees.