Vireos are stocky songbirds with sturdy, hooked bills. They tend to be drab in colour, usually green above and whitish or pale yellow below. Females build neat, compact cup nests in the fork of a branch.
All vireos prefer a habitat of dense brush and trees. They feed on berries and insects, but different vireo species co-exist by exploiting particular habitat niches. For example, Red-eyed and Philadelphia vireos maintain separate territories within forests, with Philadelphia Vireos favouring the higher vegetation.
Despite its name, the Philadelphia Vireo is seldom seen in Philadelphia. The oldest recorded Philadelphia Vireo was at least 8 years and 10 months old when found in Guatemala in 1970. It had been banded in Ontario in 1962.
Although the Philadelphia Vireo could be vulnerable to loss of habitat, its population seems have been increasing in the past several decades. It is estimated at 4 million birds, with the great majority breeding in Canada. It winters across Central America.