Day perches of Bald Eagles wintering in ponderosa pine forests in northern Arizona.

During winter when food is scarce, Bald Eagles (Haliaeetus leucocephalus) use day perches to access limited food sources. We described individual day perches and hot spots (used by multiple birds or over multiple years) for 13 Bald Eagles wearing platform transmitter terminals in northern Arizona during winters of 2005 to 2010. We hypothesized that proximity to prey, visibility, and microclimate influenced eagles in their choice of both types of perch sites. To evaluate proximity to prey, we measured distance to sources of prey (e.g., roads, large road-killed animals, and water features). For visibility, we used measures of vegetation height, topographic position index, and crown cover. For microclimate, we considered aspect and slope. Of the perches, 55% were in Petran Montane Conifer Forests (PMCF), and these perches were compared to randomly selected locations within that forest type. We used binary logistic regression and multimodel inference to differentiate used sites from random sites. Bald Eagles selected individual perches that were closer to road-killed animal sites, lakes, roads, and roads and water features (combined) than random sites were. Bald Eagles also selected hilltops and north-facing sites with greater diversity in vegetation structure. The PMCF forest type occurs across northern Arizona along the Mogollon Rim. This habitat is probably selected most often for perching because of the concentration of prey and availability of perch sites. Tall perch trees surrounded by shorter vegetation in this forest type can provide easy flight access and panoramic views. Hot spots varied in elevation, aspect, and vegetation type but were close to potential sources of prey. Maintaining forest structure with visibility and variability in tree height in locations that are close to prey sources will provide these types of perches. [ABSTRACT FROM AUTHOR]