Wildlife Watching Wednesday: The Bay-Breasted Warbler

By: Tom Berg

The spring bird migration is underway, and warblers are heading north from their wintering grounds in the southern United States, Central America and South America. There are more than 100 warbler species in the world, and more than 50 of them can be found right here in North America. One of the more interesting species is the small Bay-Breasted Warbler.

This warbler is a little smaller than a sparrow, and most individuals weigh less than a half ounce! Breeding males are distinctive-looking with a grayish-black back and a black mask around the eyes. The top of their head is reddish-brown, as is their throat and breast. A cream-colored bar on the back of their head helps identify them. They also have bright white wing bars that are easily seen.

Bay-breasted warblers migrate through the United States on their way to the boreal conifer forests of Canada to breed. Spruce trees are favorites of theirs, especially since one of their preferred foods is the spruce budworm. Spruce budworms are small, native caterpillars of the spruce budworm moth. When there is a large outbreak of spruce budworms, the population of bay-breasted warblers increases as well.

Besides budworm caterpillars, bay-breasted warblers also hunt for other insects among the branches of spruce and fir trees. Beetle larvae, black flies and a large variety of other caterpillar species are part of their diet. Small spiders are also very abundant in the trees, and the warblers are more than happy to snap them up, too. When the warblers migrate south again in the fall, they eat fewer insects and concentrate more on berries and small fruits.

During the nesting season, bay-breasted warblers tend to build their nests about 15 feet off the ground. Other warbler species, like the Cape May warbler and the blackburnian warbler, often place their nests much higher in the tree – like 40 or 50 feet above the ground. This arrangement allows multiple warbler species to use the same trees without crowding each other. The different warbler species usually hunt for insects in different parts of the trees as well. It’s a pretty good arrangement!

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