Black-and-white warblers returned last week after wintering on Caribbean islands. Participants on several Audubon bird walks saw these interesting little birds. They usually are seen creeping across tree trunks, up and down the trunks and around thick branches, just as nuthatches do. They probe in crevices in the bark for insects, insect eggs and insect cocoons.

They have adaptations for that lifestyle. The bill is unusually long and down-curved for a warbler. It probes into cracks in the bark and comes up with food. Its toes are unusually long for a warbler, too. They function well for gripping bark. These features are subtle, but make a difference in obtaining food.

The first time I ever saw a black-and-white warbler, years ago as a “green” birder, I thought it must be a kind of nuthatch or creeper. I turned to that page in my bird book, and this bird was not there.

I checked a few other pages and gave up for awhile. The next day I checked the book again, and I did not find the little creeper or nuthatch-type bird. I had a birding mentor back then, and I told him about the mystery bird. He said with a smile, “black-and-white warbler.” Sure enough, there it was in the book, with all the other, more brightly colored warblers.

The black-and-white warbler usually prefers mature forests because larger trees have rougher bark than young trees. Rougher bark has more crevices than smooth bark. More insects can live and hide on rough bark than on smooth bark. Also, this ground-nesting species fares better where the forest floor has more features, such as pits and mounds, or fallen trees, where it can hide its nest.

Yellow warblers and hummingbirds also appeared last week, after a long migration from Central America and Caribbean islands. Male yellow warblers have russet streaks down the bright yellow chest. This species sometimes nests in shrubby areas of suburban yards, although they are more abundant in less disturbed areas.

Parula warblers arrived also, thrilling people on bird walks with their colors: blue, yellow, orange, white and green. They are colorful, small and fast-moving warblers. They too arrived from the West Indies.

Next week the neo-tropical migrants from the South American rain forests will arrive. Those who want a schedule of free bird walks may call the Fields Pond Audubon Center at 989-2591.