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Serving Northern St. Louis County, Minnesota

ON THE REBOUND?

After a steep population decline, evening grosbeaks seem surprisingly plentiful again in the North Country

Marshall Helmberger
Posted 5/24/23

Recently, it seems, we tend to have more bad news than good when it comes to the state of bird populations in North America, including right here in the North Country. But now, one of the birds that …

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ON THE REBOUND?

After a steep population decline, evening grosbeaks seem surprisingly plentiful again in the North Country

Posted

Recently, it seems, we tend to have more bad news than good when it comes to the state of bird populations in North America, including right here in the North Country. But now, one of the birds that had shown some of the most dramatic declines in numbers over the past several decades, has rebounded to a remarkable degree, at least in our region.
I’m talking about evening grosbeaks, a species whose population has declined by 92 percent since 1970, according to most recent surveys. That’s the steepest population decline of any land bird in North America and it has left ornithologists scratching their heads to figure out why.
After all, evening grosbeaks used to be among the most popular birds at feeders, at least back when they were still regulars at many feeders. Their cheery call, gregarious nature, and dramatic and colorful plumage, makes them hard to resist.
You might think that a bird that makes heavy use of feeders would be doing exceptionally well these days, when bird feeding remains an incredibly popular activity. Clearly, something else has been going on and researchers are only starting to get a handle on it.
Perhaps because evening grosbeaks were until recently quite common throughout their range, it appears they never attracted much interest from researchers. That’s changed recently since their dramatic decline has been so noticeable and, in some ways, inexplicable. At this point, researchers have little more than guesses, noting that evening grosbeaks seem to be more vulnerable to window strikes and car impacts than other species. They’ve also suggested climate change, loss of mature and old-growth forest habitat in their breeding range, as well as forest management efforts to control spruce budworm outbreaks— but as is obvious with a list this long, researchers are just speculating at this point.
An international group, known as the Finch Research Network, or FRN, which now publishes the annual finch forecast each fall (which we regularly report on here), has begun to take a closer look at evening grosbeaks, as part of a joint effort known as the International Road to Recovery Evening Grosbeak Project and they began doing some banding and satellite tagging here in northern Minnesota last year.
I spoke with Matt Young, who is spearheading the effort for the FRN, and sounds hopeful that the species is showing some signs of recovery in eastern North America, including eastern Ontario, Quebec and northern New England.
I noted in our conversation that they certainly seem to have increased in northeastern Minnesota as well in the past couple years. Many folks who regularly feed birds in our area reported unusually robust numbers of evening grosbeaks since 2021.
We’ve been feeding as many as 20 of them daily through much of the late winter and spring, and friends in Greaney have reported feeding as many as 50 through the winter. I know I spent more on sunflower seeds this winter than ever, and not just because the price of seeds has jumped. With good numbers of both pine and evening grosbeaks this winter, they would go through a 40-pound bag about every ten days.
One thing that may be helping boost evening grosbeaks in our area is the spruce budworm outbreak that has been rolling through the region over the past decade. Young said evening grosbeaks feed heavily on budworm during their nesting season and when there are outbreaks, they can have tremendous reproductive success.
According to Natural Resources Canada, spruce budworm outbreaks occur on a roughly 30-40 year cycle, so it’s possible that the 92-percent reduction in evening grosbeak numbers since the 1970s is relative to a previous peak in the budworm cycle. There are plenty of long-term cycles at play with so many species that comparing today’s population with the past can be unhelpful at times.
In fact, Young and two other authors suggest in a detailed blog post on e-bird.org that the evening grosbeak population may have been unusually high from the 1960s to the early 1990s due to significant budworm outbreaks from 1945-55 and 1968-88 in the boreal forests of Canada. At the same time, the widespread planting of box elder trees (the seeds of which are a favorite food in the non-breeding season) in the northeast U.S. appears to have allowed for significant range expansion as well into New England.
“The species’ expansion was also supported by the proliferation of pin cherry and a fondness for sunflower seeds at a growing numbers of bird feeders across the East,” writes Young and his co-authors Tim Spahr and Andrew Spencer. “In fact, for a few decades evening grosbeaks were one of the most common species seen at bird feeders across much of North America in the winter.”
That, of course, is no longer the case. Young and his fellow writers noted that Canadian forest managers have been increasingly managing to reduce budworm outbreaks, and that could be constraining the breeding success of the species.
Hopefully, some of the ongoing research will give wildlife managers a better understanding of the population dynamics at work here. This is certainly one species whose absence (until recently) has been noticed by many. I know that having robust numbers of them back at our feeders recently has been a high point in our wildlife watching. Let’s hope their comeback continues…