RESPONSES OF RAVEN AND RED-TAILED HAWK POPULATIONS TO LINEAR RIGHT-OF-WAYS

Linear right-of-ways are ubiquitous in the United States and may alter vertebrate populations, yet they remain little studied. We examined t he relationship between these areas and common raven (Corvus corax) an d red-tailed hawk (Buteo jamaicensis) populations in the Mojave Desert of California by flying helicopter transects along paved highways, tr ansmission powerlines, and control areas (i.e., no highways nor powerl ines within 3.2 km). Ravens were equally (P > 0. 10) common along high way and powerline transects, but were more (P < 0.02) abundant along t hese transects than along controls. Raven nests were more (P < 0.0001) abundant along powerlines than along either highways or controls. Red -tailed hawks and their nests were more (P < 0.0001) abundant along po werlines than along either highway or control transects. Neither speci es used potential nest or perch sites in proportion to their availabil ity. Ravens used power poles as nest sites more (P < 0.001) than expec ted based on availability, but not (P > 0.10) as perch sites. Red-tail ed hawks used power poles for both nesting and perching more (P < 0.00 1) than expected based on availability. Our data suggest that ravens a re more abundant along highways because of automobile-generated carrio n, whereas both ravens and red-tailed hawks are more common along powe rlines because of the presence of superior perch and nest sites. We re commend that land managers evaluate possible changes in vertebrate pop ulations and community-level interactions when assessing the effects o f future linear right-of-way projects.