Of a Feather: The miniature mockingbird

COURTESY of NPS N. LEWIS
Most of the birds at my feeder station are finches of one kind or another: goldfinches, purple finches, dark-eyed juncos, pine siskins, and the occasional cardinals. Their short conical beaks have evolved to crack shells to find the nutritious germ within. This adaptation, among others, allows them to remain in northern New England for the winter.

The omnivorous robins and bluebirds manage to find food around here in the colder months by going from berry patch to apple orchard and feeding on the frozen, desiccated fruit still hanging from the branches. There are a few other birds that do the same—improvise diet-wise—to get through the winter. However, there are some birds who simply do not improvise when it comes to eating. They are eaters of invertebrates and that is that. They go where their comestibles are not driven into hiding by cold or covered with snow.

Many warblers fall into this category, but so does the blue-gray gnatcatcher (Polioptila caerulea). Gnatcatchers are about the size of warblers, carry themselves like wrens, and the blue-gray species at least has the coloration of a familiar mimic-thrush and is therefore referred to as the “miniature mockingbird” (by R.T. Peterson).

In 1949, when Arthur Cleveland Bent published his “Life Histories of North American Thrushes, Kinglets, and Their Allies,” in the chapter on blue-gray gnatcatchers, written by Francis Marion Weston, they were said to be found only north to Essex County, New Jersey. This is the northwestern part of the state that borders New York and Pennsylvania.

“The Birds of New Hampshire” puts the very first (albeit suspect) state record of this species in 1900. Over the next 50 years, there were scattered sightings, but there was no record of it breeding in New Hampshire or in any of the three abutting states. The first documented nesting was at Holderness in 1965. Since then, it has become “an uncommon but increasing species in the southern half of the state, rare in the north, and uncommon breeder south of the mountains.”

Unlike the other southern species expanding northward — mockingbird, cardinal, tufted titmouse, red-bellied woodpecker, Carolina wren — the gnatcatcher is a migratory species. In the deep South it is common everywhere, but in the northern part of its range it tends to follow river valleys, the most temperate climate available. In addition, according to Weston, who spent most of his life in Charleston, South Carolina and Pensacola, Florida, although it is seen at all levels and many habitats in the South, in the northern parts of its range it tends to be a bird of the hardwood treetops.

Sandra B. Turner, writing in the “Atlas of Breeding Birds in New Hampshire,” notes that nests were found from 3 to 80 feet, but six nests were found between 30 and 60 feet up. Confirming Weston’s description of their northern habitat preference, Turner observes that the nests were found “near swamps, a pond, a brook, and the Merrimack River.”

The gnatcatcher nest resembles that of a ruby-throated hummingbird. It is affixed to a horizontal branch and is, according to H.H. Harrison’s field guide to birds’ nests, “a deep neat cup of plant down and fibers, grasses, and hair, bound with spider or caterpillar webs and covered with lichens. The gnatcatcher’s nest is about an inch larger than the hummingbird’s and its eggs are pale blue with speckles at the larger end, while those of the hummingbird are white.

Most of the gnatcatchers arrive in northern New England in May and depart in September, which corresponds with the availability of enough insect and other invertebrate prey to feed their nestlings and sustain their fledglings. Weston, in that way of Edwardian birdwatchers, provides a detailed description of the stomach contents of several dissected birds. For example, Edward Forbush, state ornithologist of Massachusetts, found “locusts, … gnats, … ants and other hymenoptera, wood-boring weevils, beetles, and spiders.”

Some blue-gray gnatcatchers remain in the U.S. through the winter, but they are mostly confined to the Gulf Coast states. Even there, they rarely come to feeding stations and are observed to sustain themselves through the colder months largely on insect eggs and pupae. The bulk of the population, however, retires to even warmer climes, as far south as Guatemala and the Yucatan peninsula of Mexico, where there are plenty of active insects, even in the winter.

Their reluctance to come to feeding stations translates on their breeding grounds to being woodland rather than backyard birds. While other southern birds, like Carolina wrens and cardinals, are in the North almost exclusively residents of settled areas, the northern gnatcatchers remain aloof.

P. caerulea is one of fourteen species in this genus; it is the most northern, most widespread, and migratory one, while three others are non-migratory species that live largely in Mexico with two ranging up into the southwest U.S. These four are slim 4 ½-inch birds with thin rapier-like bills, white on their long tails and white eye rings.

P. caerulea has white outer tail feathers (like a mockingbird). The outer edges of its primaries are black and inner secondaries are edged in white (again, somewhat mockingbird-ish). The males have black foreheads with the dark color extending to just beyond the eye. (The western sister species all have more extensive black on the head.)

If you go looking for gnatcatchers in New Hampshire, you should search in swampy lowland woods and listen for their thin nasal call, which Sibley renders as speee, szeewv, or zeewv zeef zeef. Their song is described by Turner as “elaborate” and “whispered.” Weston quotes an observer: “The song is long continued, of greatly varied rapid notes and trills, on a high pitch, and of a squeaky or nasal quality.” The males also stop singing as soon as the eggs hatch. Good luck catching sight of gnatcatchers.

Bill Chaisson has been a birdwatcher from the age of 10. He is a former managing editor of the Eagle Times and now lives and works in the town of Wilmot. Contact him at [email protected].