Rose-breasted Grosbeak

With its bright splash of pink on an otherwise black and white body, the male Rose-breasted Grosbeak is instantly recognizable when one shows up at a bird feeder. The female is brown and white with a prominent white eyebrow and looks something like an oversized female Purple Finch. Males and females share in most reproductive duties, from nest building through incubation to brooding and feeding the young. Both sexes also sing, although singing in females is primarily associated with breeding behavior (e.g., while incubating or nest-building). In this context singing may serve primarily to reinforce the pair bond rather than help defend a territory.

Rose-breasted Grosbeaks have a complex series of plumages. In their first fall, young birds typically resemble females, although males can have a a variable amount of pink or orange on their breasts. In this plumage they resemble the extremely rare Black-headed Grosbeak, which is the Rose-breast’s replacement west of the Great Plains. Although Black-headed Grosbeaks have occurred in New Hampshire they are not to be expected, and any such bird should be examined very carefully. Over the winter young male Rose-breasts start looking more like adults, but in their first summer will still be somewhat splotchy rather than sporting solid blocks of color. It may take 2-3 years for them to attain full adult plumage, although they can still breed when one year old.

The Rose-breasted Grosbeak is a bird of forested edges and mid-aged regenerating forests, and maturation of the latter may a factor in long-term declines in the eastern portion of its range. It may also be sensitive to forest fragmentation, and even if grosbeaks settle in smaller forest fragments they may be less successful in them. If breeding habitat is behind these declines, it would suggest that forests are being managed differently in the Midwest, where populations are generally stable or increasing. It’s possible that threats on the winter grounds operate differently for birds across the breeding range. Rose-breasted Grosbeaks migrate to a large area from southern Mexico to northern South America, with eastern birds wintering father east than western ones. Thus, if Columbia and Venezuela were experiencing more habitat alteration than Mexico, the effects would be most pronounced in birds from the eastern part of the breeding range. This is purely speculative however, since supporting research has yet to be undertaken, and declines in our Rose-breasted Grosbeak population remain unexplained.