The blue-headed vireo (Vireo solitarius) is a Neotropical migrating song bird found in North and Central America. There are currently two recognized subspecies that belong to the blue-headed vireo. It has a range that extends across Canada and the eastern coast of the United-States, Mexico and some of Central America. It prefers large temperate forests with a mix of evergreen trees and deciduous under growth.
As the name suggests, the blue-headed vireo is characterized by its blue-grey head and bold yellow wing bars. Both sexes are very similar in plumage and size. Juveniles also have a similar plumage.
Populations of the blue-headed vireo have been steadily increasing since the 1970s. Therefore, in 2004, the species was classified as a "Least Concern" species.
Description
The blue-headed vireo has similar plumage year round and does not drastically change its appearance during the breeding season. It can be characterized by its olive green upper body, two bold yellow wing bars down the edge of its wing, and a deep blue-grey crown from which it gets its name. The juvenile plumage of immature blue-headed vireos is not distinct but very similar to the adult plumage. While this bird's appearance is similar to the closely related Cassin's vireo (Vireo cassinii), the Cassin's vireo can be differentiated by its lighter yellow patches, a smaller, thinner bill, and a brownish-grey crown. There is little to no sexual dimorphism between males and females as both are similar in plumage colouration and size.
Like most Vireos, the blue-headed vireo is a relatively small bird with a length of . The wingspan is usually found to be around and their weight is typically . There are some subtle differences between the V.s. solitarius and V.s. alticola subspecies. V.s. alticola, the larger of the two subspecies, has a darker back with a larger wing length of and a bill length of . Conversely, V.s. solitarius is slightly smaller with a wing length of , and a bill length of .
The average lifespan of the blue-headed vireo in the wild has been measured to be approximately 7 years and 5 months.
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.
Though it had been previously classified as a separate species, the blue-headed vireo along with the plumbeous vireo (Vireo plumbeus) and the Cassin's Vireo (V. cassinii) were lumped in the 1950s into a single species, based on morphological data. This group of vireos was collectively known as the "Solitary Vireo" (Vireo solitarius). This taxonomy prevailed until 1997 when new molecular data showed that there were in fact three distinct species. The taxonomy reverted to that prior to the 1950s, and the blue-headed vireo was once again its own species.
There are two recognized subspecies of blue-headed vireo:
Vireo solitarius solitarius – (Wilson, A, 1810) – 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 – Brewster, 1886 – 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.
Habitat and distribution
Native to North America, the blue-headed vireo enjoys a large breeding range that extends over an immense area of Canada and northern United States. The breeding range of V.s. solitarius extends from northeastern British Columbia across Alberta, Saskatchewan, Manitoba, Ontario and Quebec and down to southern Pennsylvania and New Jersey. V.s. alticola has a distinct breeding range that includes western Maryland and south, mainly in the Appalachian Mountains, to northern Georgia. At the end of the breeding season, the blue-headed vireo migrates south to its overwintering area. V.s. solitarius has the longest migration of the two subspecies and inhabits an overwintering area that includes eastern and southern Mexico to northern Central America. V.s. alticola migrates across a shorter distance to an area that extends from southeastern Virginia to Texas.