High-Frequency Photographic Imaging Provides Novel Insights into Nesting Bald Eagle Diet and Opportunities for Public Engagement

Abstract. Bald eagles (Haliaeetus leucocephalus) were formerly endangered in the contiguous United States, but have since recolonized much of their past range. Maintaining bald eagle populations following recovery requires knowledge of factors that influence nesting success, including food habits during the brood-rearing period. We examined over 26,000 images from a high-resolution, above-nest digital camera to document the diet of a nesting bald eagle pair in north-central Indiana, U.S.A., during the 2018 brood-rearing period. After the hatch of two eaglets in April 2018, the camera was programmed to take still photos of the nest every 20 min, in addition to live-streaming video to YouTube for public audiences. Still images were used to quantify and identify all prey deliveries to the lowest taxonomic level possible, typically species. A total of 135 prey items and at least 26 prey taxa were recorded during the 75 d of the study, although daily prey count became uncertain in the final 20 d as fledglings began to move out of camera view. The majority of recorded prey items (73%) were fish, with redhorse suckers (Moxostoma spp.) representing the most numerous of the 13 fish taxa observed. Smaller numbers of birds (13%), mammals (10%), and reptiles (4%) were also observed. Although our results represent one nest across a single brood-rearing season, we gained novel insights through the analysis of high-frequency, high-definition images that provided increased temporal and taxonomic resolution of prey deliveries. The use of a camera not only avoided historical biases in bald eagle diet analysis, but also provided a valuable tool to engage public audiences.