The Nashville Warbler passes through Edmonds on its way to breeding sites in the Cascades and other mountain ranges of Eastern Washington. Look for it in second growth forests in summer. In May it can pass through any of the forested parks of Edmonds. Although it is not reported every year in Edmonds, it is regularly seen in the mountainous regions of Snohomish County.
Insects are the heart of a Nashville Warbler’s diet. Adults consume aphids, beetles, grasshoppers, caterpillars, leafhoppers, and other insects, including eggs and larvae. Nestlings are fed flies, small beetles, caterpillars, and other insects. This warbler forages mostly in the lower parts of trees, both in open woodlands and in thickets at forest edges. It gleans insects from twig tips, the undersides of leaves, and from catkins and flowers in trees.
Breeding behavior of the Nashville Warbler has not been well documented. Males certainly sing from perches once on their breeding territories and will sometimes sing while engaging in a slow, hovering display flight. Once a pair is formed, the warblers build their well-hidden nest on the ground, in a depression made in vegetation such as club mosses under scrub bushes or saplings. The nest is an open cup made of bark strips, coarse grasses and ferns. It is rimmed with moss and lined with fine materials such as animal hair, fine grasses, or pine needles. The female does most of the incubation of her 4-5 eggs, but the male will help out. While she incubates the eggs for 11-12 days, the male brings her food. Both adults will feed the nestlings who remain in the nest for about 11 days after hatching.
The Nashville Warbler does not breed in Tennessee. So why is it called Nashville Warbler? Alexander Wilson first observed it near Nashville in 1811, as it was passing through in migration, and so named this warbler. There are two subspecies, ruficapilla in the East and ridgwayi in the West. The western subspecies was formerly thought to be a separate species and carried the common name of Calaveras Warbler. The oldest Nashville Warbler of record was a male, ten years and two months of age when he was recaptured and re-released in an Ontario banding operation. There are a number of collective nouns for any group of warblers, including bouquet, confusion, fall, and wrench.
For conservation purposes, the Nashville Warbler rates a low concern. The population is stable, having experienced only a slight decline between 1966 and 2014. The global population is estimated at 32 million, with 19% spending part of the year in the U.S., 81% in Canada, and 89% in Mexico. The species may have benefited from human activity, in that logging has increased its preferred habitat of second growth forests.
The song of the Nashville Warbler can be heard here: https://www.xeno-canto.org/340669.
— 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.