Introduction

A large, unwary finch, the Pine Grosbeak inhabits subarctic and boreal forests from eastern Asia to Scandinavia and, in North America, from eastern Canada to western Alaska. It also breeds in coniferous forests of western mountain ranges and in coastal and island rain forests of Alaska and British Columbia. To most North Americans, this species is an infrequent winter visitor; it irrupts less frequently than other boreal cardueline finches, and its flights seldom penetrate as far south. Only during exceptional winter irruptions does the Pine Grosbeak become conspicuous, and then only locally in southern Canada and the northern United States, where it feeds primarily on a variety of buds and the seeds of mountain ash, box elder, and ash. In western mountains and coastal forests this finch apparently does not irrupt and is seldom encountered more than a few kilometers from its breeding habitat.

Pine Grosbeaks are most abundant in open forest, a condition occurring near treeline in taiga and montane forests, and near natural and human-made openings elsewhere. Another correlate of abundance is water; wet, high drainages are good places to find Pine Grosbeaks in the Rocky Mountains. A short, conical bill allows this species to nip buds and growing tips of conifer branches and to crush seeds, although it feeds its young mainly on insects captured on the ground, in vegetation, and by fly-catching.

This species varies considerably in body size, plumage color, and bill size: across the taiga, variation is clinal, with a trend toward larger body and proportionately shorter bill in the Northwest and in northern Quebec. From Arizona north into northern British Columbia, individuals are smaller in body size. Birds of the Sierra Nevada, Queen Charlotte Islands, and coastal Alaska are distinctive in body size, plumage color, and bill dimensions.

Most references to this species have dealt with winter irruptions. An early study by Ray (1912) in California revealed much about habitat ecology and breeding biology. More recent key studies of geographic variation in body size and vocalizations in North America (Adkisson 1973, 1977a, 1981) and of breeding biology and nutrition in Finland (Pulliainen 1974, 1979; Pulliainen and Hakanen 1972) leave many unanswered questions about basic demographics, habitat ecology, physiology, and the causation and timing of irruptions. The ease with which this species can be kept and bred in captivity (St. Quintin 1906, Adkisson 1981) makes possible research in environmental and reproductive physiology and the biochemical bases of pigment synthesis.