Woodland Birds, Pacific Northwest
The wilsons warbler is a very common bird on the south island. Wilson’s Warblers are small yellow birds marked with black. They are bright yellow below and an olive-yellow above. Males have distinctive black caps on top of their heads, and both sexes have large, black eyes that stand out against the bright yellow on their faces. Females and immature youngsters have dull dark caps.
In the spring, they usually arrive earlier in the mountains than in the boreal region. The Wilsons warbler is southbound by mid-August and winter in Central America. Migrants are fairly common in both spring and summer in southern parts of Vancouver Island. Habitat requires prominent under-story and heavy scrub. Alder and willow thickets in forest edges and clearings are favorable.
This species gleans and catches small invertebrates in the middle to low levels of the canopy. They will also eat fruit and berries.
Wilson’s Warblers are primarily monogamous, although some are not, and high rates of extra additions to pairs have been observed. The female builds the nest in a patch of moss, low shrub or on a low branch. She builds a cup-shaped nest out of leaves, grass, and moss, and lines it with grass and animal hair. The female lays up to 7 eggs and incubates them for about 12 days, she broods the young for the first few days after they hatch, then both parents will feed the young for about 25 days, the young ones leave the nest when they are about 10 days old.
Wilson’s Warblers are migrants that winter in the mountains of Central America, although some of them remain in the southern states. They fly at night when migrating, usually alone or maybe in small groups, sometimes in mixed groups.