A small, drab, undistinguished bird, the warbling vireo (Vireo gilvus) spends hours singing high in the tree canopy. It is often its call that brings attention to this active forager as it works the treetops gleaning insects from leaves. Recently at Manzanita Lake in Lassen Volcanic National Park I heard the warbling vireos in the ponderosa pines above me before I saw them. Warbling vireos are constantly on the move as they search for insects. After about twenty minutes spent attempting to obtain a good photograph of these active, tiny birds I decided a mediocre picture would suffice.
Warbling vireos are grey with brownish or greenish tones above and whitish below, occasionally with a yellow tinge to the flanks. The face pattern, which may be faint, is a dusky post ocular stripe, white eyebrows, a greyish line through the eye and white lores. The bill land legs are dark.
Migrants, warbling vireos winter in Mexico and Central America and breed throughout most of the United States (except the extreme south east) and Western Canada. Some feel that eastern and western warbling vireos may represent two different species, while perhaps two subspecies make up the western population. Generally western warbling vireos are smaller, have upper parts that are more olive green and have smaller bills and a darker crown than their eastern counterparts.
Warbling vireos live in mixed open deciduous woodlands or coniferous forests, particularly near streams, lakes, ponds or other water. They also can be urban residents inhabiting parks and gardens. In the winter when insects are scarce warbling vireos will eat fruit. If a caterpillar or other large insect is caught, the warbling vireo will hit its prey against its perch until the unwieldy insect is subdued or killed.
Warbling vireos are interesting to watch and hear, even if they are not interested in posing for photographs.