We are fortunate here in the Pacific Northwest to have a large population of what are called “wood warblers” and the Wilson’s Warbler is one of the brightest colored, and therefore one of the easiest to spot. The only problem is developing “warbler neck,” a general soreness from having to constantly tilt one’s head back while searching for the birds in the overhead canopy. Also to be avoided is the too-quick snapping of the head while trying to follow this sprightly little jewel of a bird as it zips from leaf to leaf. I’m serious. You just try it for a few hours.
Size: On the Pacific coast, they are a bit smaller than the western-central and Alaskan birds; 4.5 inches tall, with a wingspan of 5.5 inches, and weighing about 0.4 ounces.
General Description: The breeding male Wilson’s Warbler has an olive-green back and bright yellow below, and a dark black cap. The breeding female also has a dark black cap but isn’t quite as bright as the male, and the juveniles are duller with a cap not as dark as the adults. The Pacific coast birds also have the brightest yellow-orange foreheads and faces. It is easily distinguished from other olive-green warblers by the lack of wingbars, streaks, or tail spots.
Habitat: These warblers are found in dense, moist willow and alder thickets in natural clearings, logged clearcuts, avalanche chutes, stream corridors, or wetland edges. They breed in wet, shrubby areas within forests.
Behavior: Wilson’s Warblers are mostly solitary outside the breeding season, but they also forage in mixed flocks, gleaning prey from leaves and twigs, and even flying out to capture insects from the air. The bird seems to have no fear of humans, so can easily be seen in the canopy and nearer to the ground. They also have a distinguishing tail flip. During early summer the male often bursts into song, several of which can be heard here: http://birds.audubon.org/birds/wilsons-warbler
Diet: Though mainly an insect eater, including beetles, bees and caterpillars, this warbler also eats berries.
Nesting: In the Pacific lowlands, Wilson’s Warblers are primarily monogamous, though high rates of extra-pair mating have been observed. Pacific lowland populations nest in shrubs, lay fewer eggs, and raise fewer young than their ground-nesting highland relatives. In late-April, early-May, the female selects the nest site in a low shrub or vine and builds a bulky open cup of leaves, grass, and moss, lined with fine grass and hair. She incubates two to seven eggs for 11 to 13 days, then broods the young for a few more days. Both parents feed the young, which leave the nest nine to 11 days after hatching. The parents continue to feed the young for up to 25 days after fledgling. The Brown-headed Cowbird often lays eggs in the Wilson’s Warbler nest, pushing out the warbler eggs and forcing the warbler to work that much harder to care for the much larger young of the cowbird.
Migration Status: Wilson’s Warblers winter in tropical regions in evergreen and deciduous forests, cloud forests, plantations, mangroves, and is the only migrant warbler found in tropical high plains. They migrate at night, alone or in small groups, and often in mixed species flocks.
Conservation Status: According to the Breeding Bird Survey, the population in Washington has shown a significant decline since 1980. The most significant cause is habitat degradation, especially in western riparian habitats (creek or river banks, or lakes). Some damage can be blamed on the increase in cowbirds, and some blame the pesticides still being used to control insects eaten by the birds.
Where and When to Find in Grays Harbor: Wilson’s Warblers are one of the most common breeding warblers in western Washington and can be found from April through September. Look for them in cool, moist places along the edges of forests, parks, and even your own yard if you have enough of the shrub and willow thickets they prefer. If you stand still, they may even come close enough to study you as closely as you study them! Better yet, set up an outdoor lounge chair close to their favorite habitat and observe them in comfort.