The Black-throated Gray Warbler is a short-distance migrant that winters in Mexico in pine-oak woods and dense thorn scrub. It arrives on its breeding range in the Western U.S. and a small part of British Columbia starting in March. This warbler usually shows up in Edmonds by late April. The male arrives first, often seen in the canopy of tall deciduous trees. With his black throat patch, the male might at first be mistaken for our resident Black-capped Chickadee, until you hear his song or get a better look. The female arrives a little later and has a white throat.
This warbler is not known to nest in Edmonds. Places to look for it in spring and fall migration include the Willow Creek Hatchery, Yost Park, and Southwest County Park. After passing through, it seeks out its breeding grounds in dry conifer forests and mixed woods that include oak, juniper, and pinyon pine. It can also be found in manzanita thickets and chaparral. It prefers open areas such as forest edges or dry hillsides and canyons.
Diet of the Black-throated Gray Warbler is not well known, other than that it eats mostly insects. It is known to prefer oakworms and other green caterpillars. On its breeding territory, it searches for insects among the leaves of low-growing plants. It will also hover briefly to pick insects from a variety of surfaces or fly out from a perch to pluck flying insects.
In larger trees, such as fir or oak, the nest is located on a horizontal branch, 4-10 feet from the trunk. In smaller trees or shrubs, it is closer to the trunk. The nest is usually 7-35 feet above the ground. It is an open cup of weeds, grasses and plant fibers, probably built by both sexes. It is lined with soft materials such as feathers and fur. This warbler has one brood per year. There are usually four eggs, incubated by the female for an unknown number of days. Both parents feed the nestlings. The age at which the young leave the nest is not known.
The population of the Black-throated Gray Warbler is estimated at 2.4 million. Even though its numbers declined by about 1.5 percent per year from 1966 to 2014, which is a cumulative decline of 52 percent, it is considered a species of least concern. It is a U.S.-Canada Stewardship species that has not recently been on the birds watch list because it is not one of the 33 species whose populations are in steep decline. The 2014 State of the Birds report can be seen here.
You can hear the Black-throated Warbler’s song here: http://www.xeno-canto.org/175374.
— 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.