Return of Bird of the Week: Townsend’s Warbler

Female Townsend’s Warbler, Fairbanks, Alaska

This species has a special place in WC’s heart: not only is it beautiful; it was the logo bird for the late, lamented Alaska Bird Observatory, appearing on everything from coffee mugs to stickers to t-shirts. In Interior and Southcentral Alaska, it is associated with stands of mature white spruce. That preference seems more closely associated with nest site selection than foraging, but the species is poorly known for a North American wood warbler, so the conclusion is uncertain.

The remaining white spruce forests of the White Mountains in central Interior Alaska are its northernmost breeding area; in migration to it returns to the central mountains of Mexico and as far south as Costa Rica. It’s probably most common in the forest plateaus of British Columbia and into western Alberta, but is a distinctly western species.

Female Townsend’s Warbler, Fairbanks, Alaska

In its breeding range and in migration, it feeds mostly on insects gleaned from branches and leaves to trees and shrubs of the understory. In winter range, it often exploits honeydew excreted by sap-sucking insects.

The systematics of wood warblers were recently updated. As a result, many Wood Warblers are now in a single genus, Setophaga, a total of 34 species, making it by far the largest genus, and the former genus Dendroica has been abandoned. In the case of Townsend’s Warblers, there are presently no recognized subspecies, although there are ornithologists who suggest there may be two.

The nest site is selected by the female and she builds the nest as well, usually concealed between closely stacked evergreen limbs. There are 3-5 eggs. Only the female incubates the eggs, for 11-14 days. The female broods the hatchlings 2-3 days. Both adults feed the nestlings, almost exclusively insects and other invertebrates. The hatchlings fledge in 9-11 days, but the adults continue to feed the fledglings; the interval isn’t known.

First winter Townsend’s Warbler, Fairbanks, Alaska (early August)

There is very little data on populations, survival, lifespan or causes of mortality for this species. The tendency of Townsend’s Warblers to hybridize with both Hermit Warblers in Washington and Oregon where their ranges overlap adds an additional challenge to counting the population of this species. Based on the limited Breeding Bird Survey data that is available, the population is decreasing slightly across its range, probably because of loss of both breeding and wintering habitat. The IUCN, as of 2020, classifies this as a species of Least Concern.

For more bird photographs, please visit WC’s bird photo site, Frozen Feather Images.