Evening grosbeaks are a rare ‘invader’ to spot

In the winter of 1996, I wrote: “It’s been a grosbeak winter.”

I haven’t been able to repeat those words since.

Evening grosbeaks were once a winter visitor that appeared in great numbers one year and then were totally absent the next. Only their unpredictability was predictable.

I observed the same erratic pattern of winter occurrence when I lived in Oklahoma in the early 1980s.

Among the membership of the local Audubon society, it was always big news when grosbeaks descended on Stillwater. Maybe they’d stay for the Christmas bird count, we’d hope.

Their looks

Evening grosbeaks are easy to recognize and hard to miss. They are husky finches, chunkier than cardinals, with a huge, lightly colored bill and a short, dark tail. Yellow is the dominant color. They suggest a goldfinch on steroids.

Males sport a bright yellow forehead and eyebrow stripe. The belly and rump are bright yellow. In flight, which is distinctively undulating, black wings are set off by large white wing patches.

Females are duller with a wing pattern similar to the male’s, but the contrast between the black and white is muted. Evening grosbeaks nest in the coniferous forests of the Rocky Mountains, southern Canada and the northern tier of states in the Midwest and Northeast.

During the nesting season, they feast on deciduous buds, berries and spruce budworms. Their favorite winter foods are the seeds of conifers and maples. The number of seeds trees produce from year to year varies greatly.

Such an unreliable winter food supply compels evening grosbeaks (and other birds such as red-breasted nuthatches, pine siskins, purple finches, and redpolls, which depend on similarly unpredictable winter foods) to wander in search of winter food during lean years.

Fly south

They move south until they find seed-laden conifers and boxelders (a type of maple and a grosbeak favorite) or bird feeders stocked with sunflower seeds.

And there they’ll stay, roaming from yard to yard, neighborhood to neighborhood or even town to town, gorging themselves on the easy pickings provided by their human benefactors.

Ornithologists call these erratic southern movements “invasions” or “irruptions” and refer to these species as “irruptive migrants.”

Though grosbeak invasions are natural events, there are probably exaggerated by our penchant for feeding birds and by the popularity of boxelders being planted in eastern cities as ornamental shade trees.

From the 1890s through the 1980s, the grosbeak’s winter range steadily expanded east and south. Prior to the 1890s, they were unknown east of the Great Lakes. Today, however, they seem to have reduced the extent of their southern winter wanderings.

Big beak

After one good look at a grosbeak, it’s easy to understand why they like sunflower seeds. As the name suggests, a grosbeak’s bill is enormous — perhaps even proportionately larger than a cardinal’s.

It’s the ultimate seed-cracking bill. At feeders grosbeaks are fun to watch because they can be very aggressive. They seem to prefer open trays or seed that is simply cast upon the ground.

Grosbeaks hold their place at the feeder by opening their bills and lunging at other birds that violate their “personal space.”

Sometimes they spend more time jousting than eating. But even a nattering flock of grosbeaks can consume an amazing amount of seed in a single day. As feeding birds has become more popular, well stocked feeders could at least partially explain why we now see so few grosbeaks.

I’ve seen none since 1996, and the 10-year average for the Pittsburgh area Christmas Bird Count, for example, is zero. Seven were reported in 1993, two in 1990, and one in 1986. The 1985 count of 244 grosbeaks in the Pittsburgh area is the last big count.

When evening grosbeaks find feeders to the north supplied with sunflower seeds, perhaps there’s no need to move further south.

Drop a line

If you see any evening grosbeaks this winter, especially large flocks, let me know.

Current data from Cornell University’s Lab of Ornithology Project FeederWatch indicate that few grosbeaks have been seen south of New York state and the Canadian border this winter. Historical results suggest that flocks of 25 or more grosbeaks in these areas peaked more than 20 years ago.

(Send questions and comments to Dr. Scott Shalaway, RD 5, Cameron, WV 26033 or by e-mail via my website, http://scottshalaway.googlepages.com.)