It’s finally happening. Evening grosbeaks are invading southward. They’ve been popping up all over Maine for the last month.
As a self-appointed expert who writes a birding column, I get asked a lot of bird questions. Most are about unusual identifications. Many are about pigment-challenged birds with bizarre white patches. One question I get asked a lot is this: what happened to all those evening grosbeaks I grew up with?
The question you should be asking is this: Why were they ever here in the first place?
When discovered, they were birds of the northwest. Eastern colonists were completely unfamiliar with them. In the early 1800s, they were first spotted in the Rocky Mountains. They were later described for science in the Pacific Northwest. Evening grosbeaks slowly moved eastward, reaching Toronto by the 1850s. Large winter flocks invaded New England by the end of that century, but the first New England nest wasn’t found until the year I was born, which wasn’t that long ago. (That’s my story and I’m sticking to it.) Suffice to say, they weren’t in Maine until recently.
English-speaking pioneers called them evening grosbeaks. The name given to them by French voyageurs was more accurate: the wandering grosbeak.
The reasons for eastern and southern expansion of the grosbeak range are speculative but rational. For certain, their numbers rise and fall with spruce budworm outbreaks. It’s likely that they followed budworm infestations eastward across Canada. Unquestionably the period when grosbeaks swarmed our feeders coincided with the widespread budworm outbreak of 30-40 years ago.
They are prodigious seed eaters, able to exert 100 pounds of pressure per square inch on a seed husk. By comparison, you can only manage about 60 psi on your back molars. Although evening grosbeaks are generally denizens of conifer forests, they are fond of maple seeds. Perhaps the food supply of maple seeds increased as the eastern forest changed with the demise of the American chestnut.
Backyard bird feeding probably had something to do with expansion. One noteworthy grosbeak was observed to eat 96 seeds in five minutes. Road salt probably contributed. Evening grosbeaks are renowned for picking up salt wherever they can get it, and the increasing use of highway salt over the last half century would have created travel corridors for birds wandering south.
Then they disappeared again. Backyard bird counts and Christmas bird counts have documented a 78 percent reduction in evening grosbeak numbers since 1967. Only the northern bobwhite has declined more. While the decline is likely linked to the retreat of spruce budworm, there are probably other factors. Climate change isn’t helping. They are boreal forest birds, and warmer weather is not kind to them or their natural food supply. We do still have some breeding in northern Maine, even in the leanest years.
You’d think a bird this large and yellow would be easy to locate and study on the nest. Think again. The females are drably colored, and they hunker deep in the nest where they are hard to spot. Grosbeak bills are the color of bone in winter, but they make a remarkable transition in spring, turning the exact color of new leaves and needles. They blend in. We know surprisingly little about nest productivity.
Nonetheless, evening grosbeaks are headed this way again. The spruce budworm is a cyclical pest, invading every 40 years or so. It is now well established in New Brunswick. We’re starting to see more grosbeaks in Maine this winter, as their increasing numbers in Canada force some of them south for more food and less competition. Even this behavior is cyclical. Conifers in the northern forest tend to produce big growth one year, and big seed crops the next. Evening grosbeaks are forced south by food shortages every other year, a fact noted by feeder watchers ever since the early 1970s.
There’s plenty of natural food around for evening grosbeaks right now, so they’re not coming into feeders very much yet. I’ve been noticing them mostly because they are noisy, with a screech only a mother could love. It’s something like nails on a chalkboard, but from high in a treetop. Like most birds in traveling flocks, they talk to each other a lot, giving away their locations.
There is one last bit of irony: evening grosbeaks forage all day, and they generally head to roost well before sundown. As a result, there is one time of day they are unlikely to be seen. Evening.
Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at duchesne@midmaine.com.