Red-eyed Vireo

This little bird was omnipresent during my time at Acadia National Park… but nearly impossible to actually see. We could constantly hear them calling from high above in the treetops, but with how small they are it was difficult to see them. My father in particular was really trying hard to at least see one once the whole trip.

I think this one is the only one I saw! It was very high up the tree and not a great photo, but I got the shot all the same!
Wikipedia
Audubon