The Vivacious Vireo’s Verbal Volleys
by John Trott, Contributing Columnist

Stand in the cool shade of a wood of oak, hickory and maple, and the birdsong will drift down through the trees: a series of abrupt phrases as if the bird is asking himself questions and answering them. Even in the dog days of August, when the world pants with breathless heat, the Red-eyed Vireo sings his short, sharp phrases — see me, I’m here, up here, look here — as many as forty times a minute all throughout the day. Even in the afternoon hours, when summer temperatures soar and other birds are silent, the vireo sings on and on.

My North Carolina aunt called the Red-eyed Vireo the "Preacher Bird." She interpreted the vireo as singing in preacher-like phrases: You-see-it, You-know-it, Do you hear me? Do you believe it?

One researcher discovered that the Red-eyed Vireo sang its abrupt phrases 22,197 times in one 10-hour summer day.

After a diligent search for the source of the song, the bird watcher may be rewarded with the sight of an olive-green, five-inch bird, with a white breast, gray cap, and distinct, black-bordered, white line over its eye. The ruby-red eye is only visible if one is very close. For the first year of its life, a vireo’s eye is brown.

The Red-eyed Vireo, like other members of its family, tends to stay on perch and slowly, systematically search the surrounding foliage for insects, particularly tiny caterpillars. So well does the bird’s green plumage blend with the surrounding leaves that one may have been looking at him without knowing it until he moves.

The Red-eyed Vireo belongs to a small, distinctly New World family of birds, most of which are indigenous to the American tropics. All vireos are small, greenish in hue, and have a slight hook at the end of the bill.

A unique quality of the vireo family is that they all build basket-shaped, pendant nests suspended between two forks of a sapling. The intricately woven nest of the Red-eyed Vireo is 21/2 inches deep and is constructed of fine grasses, rootlets, strips of grapevine bark, and paper from wasps’ nests cleverly bound together with webbing from tent caterpillars and with spider’s silk.

These nests are rarely seen when in use, for they are cleverly camouflaged among a tree’s foliage. When trees lose their leaves in autumn, they become apparent and one wonders how it was missed during summer.

Many years ago, I found a nest hanging from a dogwood tree in a public park in which large pieces of facial tissue were woven. When it rained, the tissue became sodden and the eggs fell through the bottom of the nest. So much for a vireo taking advantage of modern society.

The Red-eyed Vireo nests in all parts of the United States except the arid Southwest. On arriving on breeding grounds in late April or early May, the vireo has made a long, hazardous and nocturnal flight through Central America and Mexico from its wintering territory in the area drained by the Amazon River in South America.

The Red-eyed Vireo often incubates an egg that has been laid in its nest by the parasitic Brown-headed Cowbird. The cowbird egg hatches into a very hungry and demanding nestling. The larger, more aggressive young cowbird demands and receives the insects brought to the nest by vireo adults, whose own young are starving.

Initially, the Brown-headed Cowbird associated with herds of buffalo that roamed through the grasslands of the prairie states. It was a symbiotic relationship: cowbirds relieved bison of ticks and fed on the insects flushed from prairie grasses by the movements of these big mammals.

A bird following herds of buffalo has no time for nest-building, incubation and feeding of young. The cowbirds sought out and found the cleverly hidden ground nests of prairie birds, where they laid their eggs and left the raising of young to host species.

As European settlers moved west and cleared forests for their crops, cowbirds moved east to occupy new areas of open fields. They laid their eggs in the nests of smaller species such as the Red-eyed Vireo.

Three hundred years is not a long time for evolutionary changes in behavior that enable vireos to cope with a new predator. Eastern birds have not evolved strategies to enable them to avoid incubating the cowbird egg and raising the demanding young. Some species have been known to bury the foreign egg in the lining of the nest, add a new lining, and lay another clutch of eggs. Others, such as the catbird, throw the speckled egg from the nest.

As recently as 1966, ornithologist Chandler Robbins, author of Birds of North America, declared the Red-eyed Vireo "the most abundant bird in eastern deciduous forests." This is no longer true. Increased cowbird predation, fragmentation of woodlands and — possibly most decisive — the loss of winter habitat in the tropics, have taken a toll on vireo populations.