A tiny burst of yellow with a blackish to black skull cap and an olive-green back, is the Wilson’s Warbler. It is one of the most common migratory warblers in the Western U.S. It is a common summer resident and migrant in Western Washington that can be seen from April through September. LeRoy recently caught the bird in his photos near the Point Edwards pond. Look for this warbler in Edmonds in areas with deciduous trees and brush, including riparian areas. That means the Willow Creek Hatchery, the marsh and Yost Park, among other locations.
Diet is mostly insects, as it is with other warblers. It includes aphids, caterpillars, bees, wasps, beetles, and some spiders. The Wilson’s Warbler sometimes eats berries. It usually feeds within 10 feet of ground, actively searching among foliage. It will also hop on the ground, probing among fallen leaves and will fly out from brush or trees to catch flying insects in midair.
The nesting population along the Pacific Coast tends to lay fewer eggs and raise fewer offspring per nest. The mountain population lays more eggs per clutch and fledges more young. The female builds a nest that is a bulky open cup of dead leaves, grass and moss. She lines it with hair and fine grass. She incubates her 4-6 eggs for 10-13 days. Both parents feed the young, which leave the nest anywhere from 8-13 days after hatching. The Wilson’s Warbler is vulnerable to cowbird parasitism. That means the Brown-headed Cowbird regularly lays eggs in the nests of this warbler. A young cowbird is larger and can outcompete its warbler nest mates for food.
The oldest known Wilson’s Warbler was a male, 8 years and 11 months of age when he was recaptured and re-released at a California banding operation.
Wilson’s Warbler is considered to be a species of least concern. Although it is a species in steep decline (a cumulative decline in population of 61 percent between 1966 and 2014), it still has a breeding population estimated at 60 million. Leading causes of decline are thought to be degradation and loss of breeding habitat such as western riparian woodlands.
There are many collective nouns for any group of warblers. They include bouquet, confusion, fall, and wrench of warblers.
You can hear the Wilson’s Warbler song here: http://www.xeno-canto.org/302422. We are now at the time of year when many species are transitioning back to their calls or chip notes. Go to this link to hear what the Wilson’s Warbler call sounds like: http://www.xeno-canto.org/297467.
— By Carol Riddell
Carol Riddell manages the bird education displays, on behalf of Pilchuck Audubon Society and Edmonds Parks & Recreation, at the Olympic Beach Visitor Station.