Another distinctive marking of the "Philadelphia Vireo" is the dark line through the eye to the base of the bill. This sparrow-sized bird has no wing bars. It's hard to spot in the spring because this vireo arrives during the last weeks in May when foliage is already dense, and he rarely sings during migration.
The "Philadelphia Vireo" breeds in southern Canada and in the northernmost United States.
Calls or song.
This bird sounds like the "Red-Eyed Vireo", but sings the abrupt, double-noted phrases slower, less often and in a higher pitch, "See-me? Here I am! Up here. See me?"
Population and distribution.
Summering well to the north, the "Philadelphia Vireo" winters in the tropics. It was first described by John Cassin in 1842 from a specimen collected near Philadelphia, but it is by no means confined to that area.
This vireo builds a hanging nest of bark and vegetable fibers, lined with bits of lichen and thistledown. Here the female "Philadelphia Vireo" lays four brown spotted white eggs.