The Wilson's Warbler is a small, plump wood warbler with a dainty bill. The male has mostly olive-yellow upper parts with the darkest color on the wings. He sports a black crown that emphasizes a yellow face. The under parts and throat are bright yellow. His legs are pinkish and his eyes are black. The female is similar to the male but her crown is dark olive in color.
These cute, cheerful birds breed across Canada and the western United States. In the Pacific Northwest, preferred breeding grounds include young conifer, maple and alder forests as well as scrubby patches of blackberry.
During non-breeding season, a variety of habitats are utilized from lowland thickets near streams to high-elevation cloud forests. The Wilson's Warbler is one of the few migrant warblers that uses high-elevation treeless plains (paramo) in Costa Rica.
The Wilson's Warbler picks larva, spiders, beetles and caterpillars off of leaves and twigs. They also hover or sally (fly out and back like a flycatcher) to grab flies, bees, mayflies, aphids and other insects from leaves or the air. Most of the foraging is done in the understory of willows, alders and other shrubs. In winter they will also drink "honeydew", a sweet liquid excreted by scale insects as they feed on oak trees.
Except for the birds that live in coastal California areas, the Wilson's Warbler nests on the ground. The female will build a nest in small depressions on the ground usually at the base of a tree sapling, willow stem, flowering plant, dense clump of grass or log so that it is well hidden.
The base of the nest is made of large leaves or sedges. Then moss, strips of bark, fine plant material, grass and hair are added to make a cup shape.
The female will lay 2 - 7 eggs that are white to creamy white with fine reddish-brown speckles or spots. The eggs will hatch in 10 - 13 days and the chicks will fledge in 9 - 11 days. The male does help with feeding the young chicks.
Most songbird nestlings hop out of the nest when they are ready to leave and don't return. The Wilson's Warbler fledgling will head back to the nest for a night or two before finally going out on its own.
The oldest known Wilson's Warbler was a male that was at least 8 years, 11 months old. He had been banded in California in the year 2000 then recaptured and re-released in 2008
