During the breeding season, the blue-winged warbler tends to forage in the upper parts of trees and shrubs, and can often be seen hanging upside down, gleaning insects from the foliage. In dense vegetation it may also forage closer to the ground, and, during the winter, will also probe for food among clusters of dead leaves. The blue-winged warbler feeds on a variety of invertebrates, including caterpillars, crickets, beetles and spiders (2).
The breeding season for the blue-winged warbler begins with the arrival of the males on the breeding ground in April or May. The male will establish and defend a territory, posturing and chasing intruding males. Much time is spent by the male chasing potential mates, and a male usually pairs with only one female. During pair formation, the female blue-winged warbler will give a ‘Tzip’ call (2).
Nest building is carried out by the female blue-winged warbler, and the nest is usually built on or near the ground, and is well concealed using leaf material (2) (5). Between four and five eggs are generally laid, and these are incubated by the female alone, although the male will occasionally bring food to the female. The eggs hatch after 11 to 12 days, and the male provides most of the food to the hatchlings during the first few days, after which both adults feed the chicks equally (2).
A number of animals are known to prey on the eggs and nestlings of the blue-winged warbler, including snakes, birds such as the American crow (Corvus brachyrhynchos), and small mammals, including the eastern chipmunk (Tamias striatus). The adult blue-winged warbler may defend the young by mobbing a potential predator or performing ‘distraction’ displays. The reproductive success of the blue-winged warbler may also be reduced by brood parasitism by the brown-headed cowbird (Molothrus ater) (2).
The blue-winged warbler is known to live for up to seven years (2).