The Blue-headed Vireo name, formerly applied to one subspecies in the Solitary Vireo complex, now designates this recognized species, following the division of that group into three species ( American Ornithologists' Union 1997 ). The split follows recent molecular genetic studies ( Murray et al. 1994a , Johnson 1995a ) that demonstrated differences in well-recognized plumage types among Plumbeous (V. plumbeus), Cassin's (V. cassinii), and Blue-headed vireos.
The Blue-headed Vireo is widely distributed across Canada and at elevations above 400 m in the eastern United States. It is the only vireo within its range that makes extensive use of coniferous forests, although it also occupies deciduous habitats. Over most of the range of this species pairs are typically widely spaced. It prefers relatively mature and extensive forests, with an understory of shrubs and small trees where its nests are suspended well below the canopy. This vireo forages mainly at mid height in a forest, moving slowly among branches from which much of its food is secured. It is also adept at snatching insect prey from leaves and twigs while in flight.
Surveys suggest that this species has been increasing steadily in the past 4-5 decades (Sauer et al. 2011), perhaps because formerly logged forests are regenerating into acceptable habitat. Remote nesting habits and typically sparse populations in most areas, however, have hindered study of this bird. We have begun to explore foraging, breeding biology, habitat use, and behavior in some areas (James James 1978b , James 1979d , James 1981b , James 1984c , Rabenold 1978 , Sabo 1980 , Robinson and Holmes 1982 , Morton et al. 1998, 2010), although more detailed studies would be fruitful.