To figure out whether golden eagles of similar ages winter together, researchers analyzed 370,307 images collected by baited motion-sensitive trail cameras throughout eastern North America. At nine out of 200 sites with sufficient data for analysis, they documented 145 eagle visits in 2013 and 146 in 2014. As anticipated, they found variation between years in the proportion of first-winter golden eagles, but contrary to expectations, there was no age-related spatial structure in wintering populations. The lack of spatial segregation by age could mean that these eagles segregate by sex in wintering areas, or alternatively, that food availability or habitat may have been sufficient to reduce competition and explain the lack of age structure. This study shows how using trail cameras to study birds can result in important ecological insight.

Kenney, M.L., Belthoff, J.R., Carling, M., Miller, T.A., Katzner, T.E., 2020, Spatial and temporal patterns in age structure of Golden Eagles (Aquila chrysaetos) wintering in eastern North America: Journal of Field Ornithology, https://doi.org/10.1111/jofo.12325