Bay-Breasted Warbler

Setophaga castanea

We know that Bay-Breasted Warblers love to prey on Spruce Budworms (Choristoneura fumiferana). We also know that populations of these warblers fluctuate from year to year, depending on the number of budworms available. When budworm populations explode, as they do every 30 to 40 years, they can decimate millions of acres of Spruce and Balsam Fir trees. So birds like these and other warblers play an important role in a healthy forest.

Bay-Breasted Warblers enjoy similar summer habitats and diets as Cape May, Blackburnian, and Blackpoll Warblers. One strategy employed by these birds is how they locate their nests to minimize conflicts. Blackpoll Warblers nest very low (about 5 feet) in the tree, and Bay-Breasted higher (about 16 feet), while Cape May and Blackburnian Warblers nest at 40 to 80 feet.

During summer, we find these birds in Canada’s lower elevation forests from southern Northwest Territory to the Maritime Provinces and in northern New England (USA). In winter, they retreat to the West Indies, the Caribbean, Central America, and northern South America.

Modern science does not recognize any subspecies of Bay-Breasted Warblers (i.e. they are monotypic).

I first met the Bay-Breasted Warbler during spring migration on South Padre Island in 2021. It was a female. In July 2022 at Lesser Slave Lake in Alberta, I finally got to meet the rest of the family.