Migrating and Overwintering Populations of Diurnal Raptors in the Bitterroot Valley, Montana

Abstract

We identified a major spring and fall migration of diurnal raptors over a low-elevation foothills site in the northeast Bitterroot Valley. We conducted full-time migration surveys in both seasons for 2 years. Red-tailed Hawks were the most abundant species counted in both seasons. During fall migration, species composition differed from other Montana hawk watch sites located on high-elevation ridges. We used a combination of survey techniques to assess overwintering populations of raptors in the Bitterroot Valley during the winter of 2012-2013. We developed an iPad application that allows us to map fine-scale occurrence of birds and used this method to document raptor presence at the north end of the valley. Citizen Scientists affiliated with Bitterroot Audubon performed systematic, broader-scale surveys at the south end of the valley. These two methods will likely document over 3,000 raptor observations by the end of winter 2013. Rough-legged and Red-tailed Hawks comprise the majority of raptor detections. We will examine these data for spatial and temporal trends in raptor occurrence.