Evening Grosbeak Coccothraustes vespertinus Scientific name definitions

The Evening Grosbeak is a stocky, heavy-billed finch of northern coniferous forests. An irruptive migrant across much of its range, it makes roughly biannual appearances at winter feeding stations throughout much of the coterminous United States. Often moving in large flocks, this boldly colored bird with the massive bill is difficult for observers to miss. During the breeding season, however, the species is quite secretive, and courtship occurs without elaborate song or display. This secretiveness, together with a spare, flimsy nest placed high in a tree, makes it a difficult subject of study. As a result, comparatively little is known of the species' life history.

The breeding range of the Evening Grosbeak underwent a significant expansion in historic times. The contemporary scientific literature documented eastward movement, with the species regularly appearing in areas east of its known range, perhaps a result of the establishment of box elder (Acer negundo) in eastern cities as an ornamental planting. The abundant seeds of the box elder persist on the tree through the winter, providing a stable food supply. Outbreaks of forest insects may also have allowed this bird to extend its breeding range to the east.

The Evening Grosbeak was an object of much interest from the late 1800s to the mid-1900s, largely as a part of natural history and banding studies resulting from its eastward range expansion. Comparatively few recent studies have been conducted—surprising considering the species' extensive range. Important recent works include studies of breeding ecology and behavior in Colorado (Bekoff et al. 1989 Bekoff, M., A. C. Scott and D. A. Conner. (1989). Ecological analyses of nesting success in Evening Grosbeaks. Oecologia 81:67-74. Close , Scott and Bekoff 1991 Scott, A. C. and M. Bekoff. (1991). Breeding behavior of Evening Grosbeaks. Condor 93:71-81. Close , Bekoff 1995 Bekoff, M. (1995). Vigilance, flock size, and flock geometry: information gathering by western Evening Grosbeaks (Aves, Fringillidae). Ethology 99:150-161. Close ), impact on forest insect pests (Torgersen and Campbell 1982 Torgersen, T. R. and R. W. Campbell. (1982). Some effects of avian predators on the western spruce budworm in north central Washington. Environmental Entomology 11:429-431. Close , Takekawa and Garton 1984 Takekawa, J. Y. and E. O. Garton. (1984). How much is an Evening Grosbeak worth? J. Forestry 82:426-428. Close ), and winter irruptions (Bock and Lepthien 1976f Bock, C. E., and L. W. Lepthien (1976f). Synchronous eruptions of boreal seed-eating birds. American Naturalist 110:559–571. Close , Prescott 1994 Prescott, D. R. C. (1994). Intraspecific and geographical trends in body size of a differential migrant, the Evening Grosbeak. Auk 111:693-702. Close ).McBride et al. 2004 McBride, T. J., J. P. Smith, H. P. Gross, and M. J. Hooper (2004). Blood-lead and ALAD activity levels of Cooper's Hawks (Accipiter cooperii) migrating through the southern Rocky Mountains. Raptor Research 38:118–124. Close