Blue-headed Vireo - Taxonomy

Taxonomy

The Blue-headed Vireo is placed in the genus Vireo, a group of small migrating passerine birds that are characterized by their usually dull greenish colouring, and a simple, monotonous song. Members of this group are usually characterized by the presence or absence of eye-rings, eye-strips, and wing bars. There is no sexual dimorphism between sexes in this group.

Originally considered its own species, in the 1950s, based on morphological data, the two Blue-headed Vireo sub-species were grouped with the Plumbeous Vireo (Vireo plumbeus) and the Cassin’s Vireo (V. Cassinii). This group of Vireos was collectively known as the “Solitary Vireo” (Vireo solitarius). This taxonomy prevailed until 1997 when new molecular data on the “Solitary Vireo” showed that the three birds were in fact distinct species. The taxonomy was then changed back and the Blue-headed Vireo was once again its own species.

There are two recognized subspecies of Blue-headed Vireo:

• Vireo solitarius solitarius is the nominate species. It is slightly smaller and breeds across Canada to south Pennsylvania and New Jersey. It overwinters in north-central and southern Mexico.
• Vireo solitarius alticola is slightly larger than the nominate species. It breeds mainly in the Appalachian Mountains to northern Georgia. It overwinters in the Gulf States after a short migration.