Northern Yellow Warbler

Unlike most warblers, Northern Yellow Warblers occur in open brushy wetlands rather than forests, thus making them easier to see than many of their relatives. Their bright yellow coloration is an additional identification aid. Until recently this was considered the same species as the Mangrove Yellow Warbler, a non-migratory species restricted to coastal mangroves in the West Indies and Latin America. In the winter, the Yellow Warblers that breed in the United States and Canada sometimes share coastal habitats with their non-migratory cousins, but are just as likely to be found in wetlands and shrublands similar to their breeding sites.

Yellow warblers build their nests of fine bark, other plant fibers, and spider webs, giving them a silvery-gray color. While well-concealed during the breeding season, they are often easy to find in fall and winter when shrubs have lost their leaves. Brown-headed Cowbirds have no problem finding them under the leaves however, and the Northern Yellow Warbler is a frequent host of that brood parasite. The warblers usually recognize the cowbird eggs as unusual and will build a whole new nest over them and lay a new clutch. Cowbirds can be equally stubborn however, and there are records of warbler nests with as many as six layers, each containing eggs of both species.

Populations of Northern Yellow Warblers in much of the Northeast were stable through the late 1900s, only to decline sharply starting around the year 2000. Reasons for this decline are unclear, and populations in the Midwest and West don’t show it as strongly if at all. The good news is that the decline appears to have stopped in the 2010s, and even shows some sign of recovery, but overall there are certainly fewer Northern Yellow Warblers in the region than there were a few decades ago.