Worms Not On the Menu for This Bird

Those bygone biologists and naturalists who were given the task of naming the birds certainly short-changed the little Worm-eating Warbler (Helmitheros vermivorus). This warbler usually forages for its insect diet among the tree leaves – not a likely place to find worms.

The Worm-eating Warbler is a bird of the eastern United States, with Massachusetts being the northern end of its breeding range. It migrates in the fall to spend the winter among the tropical forests of Central America and the northern West Indies.

Worm-eating_Warbler_NGM-v31-p308-AIt is a secretive woodland bird found in our local deciduous forests, especially along hillsides and ravines with plenty of undergrowth. You are more likely to hear its rapid insectlike buzzing call than to actually see the bird itself. Its olive-colored back, wings and tail blend in nicely with the shadowed foliage, hiding the bird in plain sight. Once you spot its position, look for a buff-colored breast and a head with buff and black stripes to confirm your identification. Males and females are similar.

Perhaps the Worm-eating Warbler acquired this odd moniker from observations of this species consuming the worm-like caterpillars of moths from foliage. This warbler will glean insects from tree and shrub leaves, as well as from hanging clusters of dead leaves. Its slender, pointed bill is also perfect for reaching into curled leaves where insects hide.

Although it feeds in the trees, the Worm-eating Warbler nests on the ground. A cup-shaped nest of skeletonized leaves and grass is built under shrubby vegetation or other low vegetative cover. Nests may be lined with hair, and always includePolytrichium hair moss. (Possibly it was observations of birds collecting nest material from the ground that account for the worm-eating reference.)

Like many woodland birds, this species is sensitive to forest fragmentation. Surveys conducted in Connecticut and other states found worm-eating warblers in forest tracts of more than 30 acres, but sadly absent from smaller parcels. As we continue to lose chunks of forest to development, Worm-eating Warblers lose habitat vital to their breeding success.

Submitted by Cindi Kobak