Evening Grosbeak
About 140 years ago, English-speaking settlers in the foothills of the Rocky Mountains came across a beautiful big-beaked bird that appeared mysteriously from somewhere in the distant west. They named it Evening Grosbeak (Coccothraustes vespertinus is the scientific name used by ornithologists of all languages) in the mistaken belief that it came out of the woods to sing only after sundown. French-speakers named this bird more appropriately le gros-bec errant, the wandering grosbeak.

Description
The Evening Grosbeak is a plump, sturdy finch. Its body is about the size of a robin's, but its neck and its slightly forked tail are considerably shorter. Its prominent thick cone-shaped bill is truly tremendous for a bird of its size. The plumage of the adult male is spectacular, with golden yellow body feathers and a conspicuous gold band across the forehead. The underparts are yellow, and the crown and neck feathers resemble glossy, rich brown velvet. Tail feathers are jet black, as are the wing feathers except for a snow-white shoulder patch. Sub-adult males may be identified by dark areas on the shoulder patches.

Adult females are comparatively subdued in appearance. Their bodies are smoky silver-gray with areas of yellow on the sides, nape, and rump. That part of the wing lining nearest the body is bright yellow. The black tail and wing feathers have distinct white patches, and the underparts are lighter gray with undertail coverts and chin usually buffy and silvery white. By the time they are able to fly the plumage of young female and male Evening Grosbeaks resembles that of their parents sufficiently for sexual identification.

The Evening Grosbeak's bill is bone color during winter, but it undergoes a dramatic change in pigmentation in early spring. Its new color matches precisely the green of fresh deciduous buds and leaves and also the new needles that will tip the spruce boughs around the site where the bird's nest will be built a few weeks hence. The Evening Grosbeak conceals its body in the trees and in order to see lifts only its head and bill, which looks like a young green spruce or balsam cone. This is a fine example of protection through appropriate coloration.

This bird's flight is undulating. Its wing-beat is rapid with white wing patches flashing conspicuously, and the birds often call in flights.

Voice
Evening Grosbeaks are noisy and possess a wide repertoire of calls and cries. Their only song has been described as "a series of abrupt warbles" and even this is seldom heard. The most typical call is a monosyllabic chirp, which sounds very much like the chirp of the common House Sparrow, amplified. It is employed by each bird to proclaim its place in the flying flock. A lone individual or a member of a perching flock utters this same cry, apparently to advertise its presence to all within hearing range.

A wide miscellany of sounds is used to register fear, surprise, anger, pain, uncertainty, curiosity, and alarm. To discover most of these sounds one need only observe a flock closely for a few minutes at a crowded feeding tray.

Range and migration
Although four other members of the grosbeak family are found in Europe and Asia, the Evening Grosbeak is found only in North America. Its original home was the foothills of the Canadian Rockies, but its range has now spread as far east as Newfoundland. Its preferred habitat is thick coniferous forest, but it has successfully adapted to mixed deciduous habitats.
Evening Grosbeak Range Map

Evening Grosbeaks were unknown to Europeans until 1823. However, after their discovery these birds were found at points farther and farther eastward, especially in winter, until they reached the vicinity of Toronto in 1854. They seemed to appear at more and more eastern sites in winter, only to disappear again in the springtime. But the pattern was very inconsistent.

The winter of 1889-90 saw great flocks move into New England. Then few or no birds appeared in winter until, 20 years later, another heavy eastward flight occurred. At intervals since then, multitudes of this wandering species have appeared in the east and southeast until, during the winters of 1958-59 through 1960-61, Evening Grosbeaks were found as far south in the United States as Alabama and Georgia and as far east in Canada as Labrador and Newfoundland. The wanderings of western varieties of grosbeaks take them throughout much of the mountain country from western Canada to northern Mexico. The extent of the annual invasions varies from year to year, and the size of wintering populations in the East appears to have declined in the 1980s.

Biologists have traced the wanderings of some of these birds by attaching a numbered aluminum band like a bracelet around one of their legs. Evening Grosbeaks banded in Wisconsin and North Carolina have been recovered in New Brunswick and Quebec. Similarly, Evening Grosbeaks banded in New Brunswick and Quebec have been recovered in North Carolina and Wisconsin. Banding records reveal a flight tendency from west to east and south during the autumn and early winter with a reverse flight during the early spring, but these migratory movements are so variable they seem almost whimsical. They seem to be dictated chiefly by the availability of natural food and should be called wanderings in search of food rather than true migratory flights. The spreading popularity of winter-feeding stations has probably further complicated the normally erratic movements of this Gros-bec errant.

Recent studies of heavy spring concentrations of Evening Grosbeaks in Quebec and in New Brunswick have disclosed a close predator-prey relationship between this bird and that serious pulpwood forest pest, the spruce budworm. The birds concentrated in those forest areas suffering the worst incursions of the budworm. They did not return to areas where aerial spraying had eradicated the budworm, but did return to sprayed areas where the budworm still persisted. Gizzards of the adult grosbeaks in these infested regions contained large numbers of the budworm larvae and pupae, and it is thought that the parent birds fed further quantities of the larvae and pupae to their nestlings. The decline of grosbeak winter invasions in the 1980s may be tied to the end of a huge infestation of budworm in the eastern provinces.

Nesting
Despite wide popular interest in the Evening Grosbeak, very few successful studies of its nesting activities have been reported. Some nests have been found, usually 6-12 m high, in spruces, or deciduous trees. Loosely constructed of small twigs, and lined with grass, fine rootlets, or moss, the nest usually contains three or four greenish eggs lightly splotched with brown or olive.

The Evening Grosbeak's chief nesting region still seems to be in western Canada. However, this species has spread so widely that it is now almost commonplace in early summer to see adults feeding their young in almost every part of the southern boreal forest.


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