The fact that, while American Robins were the most abundant species, only the juveniles collided with windows suggests that this species has to learn about the properties of windows either through personal experience or by watching others to know that they need to avoid flying into them. One way they could learn is by remembering what windows are where in their environment, but since this is a migratory species, they would likely need to learn how to identify windows in general to notice and avoid colliding with them in new environments. Differences in learning abilities, what they need to learn about in their environment, as well the ecological relevance of windows (perhaps species that live on or near water attend more to reflective surfaces), is likely to vary by species and might help explain variation in the frequency of BWCs.