Drabbest warblers uncommon but worthy
For Mid-South birdwatchers, the arrival of the large family of wood warblers is a much-anticipated event. Some arrive at the magical spring moment when the woods are just showing green, and others show up a bit later, when the forest is fully leafed out.
These tiny spritelike creatures bring a touch of tropical color to local temperate forests, whether they come to nest and raise families or just pass through on their way north. Most species flash brilliant green, orange, blue, chestnut and especially yellow as they flit through the foliage in search of the insects that they need, either to fuel their continuing journey or to feed their nestling young. A few species, however, are inconspicuous to the point of drabness. One of these is the worm-eating warbler.
The worm-eating warbler’s name is a misnomer, since it eats no more earthworms than any other warbler species; in fact, it eats hardly any at all. It derives its vernacular name from the large number of caterpillars that can comprise up to 75 percent of its diet. When it first arrives on its nesting grounds, the worm-eating warbler forages for anything it can find to regain its strength after its long migration. It will take spiders, slugs and anything else it finds. As the season progresses, it becomes more selective, both in its choice of prey and in its foraging behavior. It searches carefully through hanging clumps of dead and living leaves, probing and gleaning for the caterpillars it prefers.
The worm-eating warbler is about the size of a sparrow. Its wings, back and tail are olive-brownish while its belly, breast, face and throat are buffy. It most notable characteristics are alternating brown and buffy stripes that run from its bill to its nape. The sexes are alike.
The habitat requirements of the worm-eating warbler are quite exacting. For successful nesting, it needs extensive tracts of undisturbed hardwood forest on moderate to steep slopes. That habitat can reasonably be expected to be found locally only among the wooded bluffs along the Mississippi River, like those in MeemanShelby Forest State Park. It is much more common in the more irregular terrain of Middle and East Tennessee.
The range of the wormeating warbler is disjunct
and fragmented. It nests from southern New England south through the Appalachians to northern Georgia and west to the Ozarks. There is also an isolated population on the Delmarva Peninsula and the North Carolina coast. As autumn approaches, worm-eating warblers all across their range depart for their wintering grounds in Central America and the West Indies, traveling mostly at night.
Worm-eating warblers return in late March to Shelby County, where they are considered “rare” to “uncommon.” Males arrive first, followed about a week later by the females. The males establish their territories by singing their distinctive, if not very noticeable song — a flat, dry insectlike trill. The male bird often returns to the same territory year after year.
The female selects the nest site. It is always on the ground, usually next to a tree or rock outcrop, often under overhanging leaves and almost always on sloping terrain, the steeper the better. She builds the nest of leaves, sitting in the open cup and arranging the nest material around her. She lays four to six white or pink eggs, which may or may not have brown speckles. The female incubates the eggs for 12 to 14 days, sitting so tightly that she will flush only if touched or stepped on. If she or her attendant mate is disturbed, they may perform a distraction display, fluttering across the ground as if injured, in hopes of luring the intruder away from the nest.
The nestlings f ledge at about 10 days and stay with their parents for about three weeks. Half the fledglings follow the male, and half follow the female. The parents will only rarely nest again.
The worm-eating warbler is a species that most casual bird-watchers in the Mid-South are unlikely to encounter. Finding one requires more than a little effort and also being in the right place at the right time. Still, it is an interesting bird well worthy of a little searching.