November 25, 2012

Birding: They're back, and most welcome: the grosbeaks

By Herb Wilson

Perhaps this winter will be the winter of the grosbeaks. In the last column, I wrote about the irruption of evening grosbeaks into central and southern Maine. Sightings continue throughout the state. Many people are seeing evening grosbeaks at their feeders for the first time in a decade or more.

We seem to have a nice influx of pine grosbeaks into the state as well this fall. Pine grosbeaks do irrupt into central and southern Maine more regularly than evening grosbeaks, but they scarcely put in an appearance in some winters.

Both of these species are aptly named grosbeaks because their beaks are indeed large, impressive tools capable of generating significant force. Just ask any bird-bander who has extracted an evening grosbeak from a mist net. But the name grosbeak is really a descriptive term rather than a taxonomic unit. Pine grosbeaks and evening grosbeaks belong to the finch family while a summer favorite, the rose-breasted grosbeak, belongs to the cardinal family.

An adult male pine grosbeak is hard to misidentify. The head, breast, sides, back and rump are a bright carmine red. The wings are mostly blackish with two conspicuous white wing bars. The belly region is gray. A pine grosbeak is much larger than a house finch or purple finch.

Females are more subtle in their coloration, but strikingly beautiful as well.

Some females are mostly gray, again with the two prominent wing bars. However, some have russet feathers on their head and rumps. Some of these birds are females, but others may be first-winter males. It is not safe to identify the gender of a russet-colored pine grosbeak.

The beak of a pine grosbeak differs from that of an evening grosbeak. The pine grosbeak bill is shorter and curved. The overall shape is more rounded than the massive conical bill of an evening grosbeak.

As with most birds, the bill and the diet fit like a hand and glove. Rather than crushing large seeds for sustenance, a pine grosbeak feeds on a variety of buds (conifers, elms and maples among others) as well as small seeds like those of box elders and ashes. Pine grosbeaks will often feed on fruits during the winter; mountain ash berries are a favorite. Apples or cherries hanging on a tree are used by pine grosbeaks. The many ornamental cherry trees on the Colby College campus are a magnet for these birds.

Like most finches, pine grosbeaks are social during the winter. Tight-knit groups of five to 10 birds form a cohesive group during the winter, often mingling with other such groups. Ornithologists suspect that each of these small groups is a family unit that has migrated together.

Pine grosbeaks are usually detected by sound rather than sight. They give a distinctive three-note flight call, sometimes rendered as tee-tee-tew. This call is strongly reminiscent of the call of a greater yellowlegs, but with a much sweeter, less harsh tone.

•••

And now another installment from the small-world department. In the last column, I wrote about the cursory observations of evening grosbeaks by the geologist Major Joseph Delafield in 1823 that led to the ill-fitting common name of this finch species. I received an email from Joseph Delafield of South Portland, the great-great-grandson and namesake of Major Delafield. Joseph has a portrait of his great-great-grandfather in his house as well as the diary from which the quotation I used was taken!

Joseph filled me in on the details of Major Delafield's career. He served as agent for the U.S. commission charged with determining the boundary between Canada and the United States. He recognized the potential mining value of rocks at the western end of Lake Superior (the Mesabi iron ore range) and negotiated the inclusion of that property as American soil.

Herb Wilson teaches ornithology and other biology courses at Colby College and perches in South China. He welcomes comments and questions at:

whwilson@colby.edu

 

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