Nature's Notebook

Our big year for winter finches continues. The unabashed star of the show has been the pine grosbeak, a beautiful, robin-size bird that feeds on fruit in winter.

The flock that had been patronizing the crabapple trees in Norfolk has, as of this writing, apparently exhausted that food supply, but another (or the same?) flock has now descended on the crabapples in the parking lot of Kent Falls State Park on Route 7.

This species is sexually dimorphic, meaning that males and females have markedly different plumages. The male is suffused with rose-red, brightest on its head and rump; its wings are grayish-black with prominent white bars. The female is mostly gray, but is tinged with a lovely golden-buff color on her head and rump. This species’ calls consist of distinctive, mellow whistles.

The name "grosbeak" was applied rather indiscriminately by early ornithologists to any bird with a large bill (the literal translation of "grosbeak"). Of the four eastern birds we call "grosbeaks," two — the rose-breastedand blue grosbeaks— are sometimes considered "true" grosbeaks and are related to cardinals and buntings, while the other two — the eveningand pine grosbeaks— are actually large members of the finch family.

Making matters more confusing, the pine grosbeak has a stubby but not very "gros" beak, especially compared to its near cousin, the evening grosbeak, which has a massive bill.

No one knows for certain what drives certain birds, often referred to collectively as "winter finches," south in periodic "irruptions" that range from a few years to seven years to 10 or more years. Like other winter finches, the pine grosbeak is normally an inhabitant of the far northern boreal forest. (Another species making a big show in our area this winter is the common redpoll.)

The most widely accepted explanation for irruptions is a shortage of food supplies in the bird’s usual habitat, and observers noted last fall the scarcity of the pine grosbeak’s favorite foods in its home range. But it seems that no one anticipated the extent and duration of this year’s southward flight, which is being compared to or may even exceed what birders call the "Superflight" of winter 1997-1998. For birders, 2007-2008 has been a winter to remember.

Fred Baumgarten is a naturalist and writer. He may be reached at fredb58@sbcglobal.net. His blog is thatbirdblog.blogspot.com.