The Evening Grosbeak is a relatively uncommon bird in southern Wisconsin, typically appearing in winter at feeders or on crops of cones. I’ve never seen the bird in southern Wisconsin; in fact, I hadn’t thought about the bird as much more than a boreal species, just reaching into the southern parts of the state around late fall to take advantage of seed crops.

My ignorance of the bird cues us into something important in ecological research: the “invisible present.” We all see the oak tree in our backyards or local parks. If that tree falls over, it’s apparent to us. But what if, during leaf out, that oak tree produced 15% fewer leaves each year…would you notice? After 5 years the tree will have lost half its leaves, and if this continued for 60 years the mighty oak tree, which could have started with 200,000 leaves, is down to a mere 14 leaves. At some point, maybe after 15 or 30 years, you might notice that the tree looks sickly or “off”, but we might be well past the point of saving the tree by then. Furthermore, your kids or grandkids might start looking at the tree when it has just 300 leaves left. By the time they’re 15 the tree might only have 30 leaves left but the change wasn’t that fast–this sadly-foliaged tree is the new normal for them.

The same sort of thing can happen with many ecological problems. For instance, with the Evening Grosbeak, its decline during the annual Christmas Bird Counts has amounted to about 15% per year, just like our oak tree. Since 2000 those numbers have leveled off to almost 0, so in my time of birdwatching a CBC without grosbeaks is the new normal. The causes of this decline are hard to pin down.

Causes of the decline might include spraying of spruce budworm in Canada, which is done for forestry practices but effectively eliminates this food source for grosbeaks and other boreal species. Other causes might include climate change, deforestation, or the structure of forests. Evening Grosbeaks did expand in the early twentieth century to the eastern US—it’s thought due to planting of boxelder trees (an important seed source)—so it could be that what we’re seeing now is a decline after a big advance across the continent.

Why grosbeak, you might ask? Gros means “thick” in French, and this bird’s beak has the ample size to crunch through thick seeds, fruits, and nuts. The males are brilliantly colored black, yellow, olive, and white with a massive beak. You’d be hard pressed to find an Evening Grosbeak at Faville Grove, but the best spot to look would be in conifer plantings or tamarack lowlands. As it stands, they’re lost to the invisible present, and the best we can do is watch, listen, and document when they might return.

Written by Drew Harry, Faville Grove Sanctuary land steward

Cover photo by Mick Thompson