I’ve seen a lot of evening grosbeaks in my life, but my latest sighting was a doozy. On a coastal road near Passamaquoddy Bay, there was a tree with so many birds in the branches, no more could fit. It was standing room only. The adjacent tree was equally full. Just down the road, a third tree had barely enough room to squeeze in a few more.
It’s been 60 years since I’ve seen so many evening grosbeaks gathered in one place. It was a commonplace sight in my boyhood. Another big wave swept through Maine in the late 1980s.
Then they mostly disappeared from our state. What happened?
The usual answer is loss of suitable habitat and dwindling food supplies. But these are unusual birds. The evening grosbeak is enigmatic — with a mysterious past.
At one time, the evening grosbeak was exclusively a western bird, rarely spotted east of the Rockies. Prior to the end of the 19th century, they began spreading eastward. One theory proposes that they followed successive outbreaks of spruce budworm across Canada. Another suggests that the increasing popularity of ornamental plantings, especially box elder, provided a new food supply.
I’m more inclined to believe the first theory, primarily because evening grosbeak populations tend to rise and fall with spruce budworm infestations. In fact, when the numbers swell, it’s one sign that there is a budworm outbreak somewhere nearby. It’s also a sign that the winter food supply up north is not very plentiful.
Winter finches crack seeds, and evening grosbeaks are mobbing birdfeeders for sunflower seeds across Maine this year. I’ve heard from many alert readers, enjoying these sporadic winter visitors. Spruce budworm is their favorite food in summer, and they are fiendishly good at finding the little caterpillars.
All finches are noisy. They typically form flocks, and noise helps keep the flock together. Evening grosbeaks are especially vocal, with a screech reminiscent of fingernails on a chalkboard. In fact, the screech is nearly the only vocalization they make. It’s one of the few songbirds that doesn’t have a song. What evening grosbeaks lack in musicality they make up for in volume. I usually hear them before I see them, even from hundreds of yards away.
Evening grosbeaks breed across Canada and down the Rocky Mountains. Small populations nest in Maine, and I see them regularly in Baxter State Park in summer. Nonetheless, we mostly observe this bird in winter. In good years it’s a regular at backyard bird feeders, and also feeds on seeds and fruit, including ornamental trees in the heart of suburbia. It’s one of the few species you will find dining on sumac.
Finches wander in winter, settling into places with ample food. Because of their nomadic nature and their irruptive behavior, it’s hard to know how many evening grosbeaks there are. Populations are certainly not as large as they were in my boyhood. It is estimated that half of them have disappeared in a shockingly short time.
The mystery deepens. There might be more than one species. Evening grosbeaks in different regions have different call notes. There are tiny but measurable physical differences in birds of each call type, notably their bill size. Some scientists have begun to ponder whether these subspecies are becoming distinctive enough to warrant reclassifying them into two or more separate species.
The same thing is happening with red crossbills, another species that is widespread throughout the northern part of the continent. Crossbills are also finches, with a similar tendency to wander in winter. However, they usually return to a home range for nesting. Red crossbills in the west have much larger bills, because the cones they need to open are much larger. There are at least ten types of red crossbills, and each can be distinguished by voice.
There are five known subspecies of evening grosbeaks. Experts can distinguish them by voice. I am not one of those experts. They all sound alike to me.
The swarms of evening grosbeaks that I encountered in childhood sparked my continuing passion for birds. It’s hard not to like a bird that is brightly colored, boisterous, sociable and tolerant of people — even curious young boys.
For now, I’ll stop worrying about the apparent decline of these cheerful birds and simply appreciate their decision to visit us this winter. When I step out to get the paper first thing on a chilly morning and hear them calling, somehow the whole day just gets a little brighter.
