My life gets complex sometimes. For instance, I was just elected to the Maine House of Representatives. As part of the campaign, I stood at the polls to greet voters for the entire Election Day. This led to three oddities.
First, by law, candidates are not allowed to talk politics at the polls. Amusingly, I had more conversations about birds on Election Day than I usually have in a month of ordinary days. I was even asked to identify cell phone photos of strange birds.
Second, strange things happen when you stand in one place for an entire day. I observed woodpeckers working methodically through the neighborhood, as if on a schedule. Then, every hour, house finches came into the maple across the street, resting for a few minutes before heading off to forage again. Why that particular maple, I wondered? Then a tufted titmouse family alighted into the same tree and foraged through. Then goldfinches. Since songbirds always keep a wary eye out for predators, clearly this tree provided better visibility than the ones near it.
Third, an evening grosbeak flew over town hall. I still see them occasionally in the northern forest, but it has been a long time since I’ve encountered one in town. There have been other reports around the state this autumn, so perhaps we will see more this winter.
Evening grosbeaks were plentiful during my childhood. Even into the 80s and 90s, mobs of them could empty my feeder in a single morning. Slowly their numbers have declined to the point where I may see three or four a year, and only if I am up north.
There is no certain answer about what has caused the rise and fall of the evening grosbeak, but there is plenty of speculation. We have lots of data, thanks to the Christmas Bird Counts run by National Audubon, and Project FeederWatch, run by the Cornell Lab of Ornithology. The former has been going on for 115 years; the latter began in the mid-1970s.
We know several things from the data. For starters, the evening grosbeak was originally a western bird. It moved eastward over the last century, first discovered nesting in Quebec in the 1940s, later found breeding in Vermont in 1953. Soon thereafter, it became abundant in northern New England and Maritime Canada. We don’t know why the bird expanded eastward, but many suspect that it was linked to outbreaks of spruce budworm. The eastern populations peaked during the worst of the outbreaks.
There are other potential factors. Evening grosbeaks rely on maple seeds for a large part of their diet. They also have a fondness for box elder. Although not native in the east, box elders were commonly planted as ornamentals during the last century. Maple seeds are still widespread, but in the industrial timberlands north of the Maine border, there has been a steady interest in planting large tracts of faster-growing softwoods. Habitat conversion doubtlessly has had an effect on grosbeak populations.
We also know historically that grosbeak invasions have been cyclical, plentiful one year, scarce the next. These two year cycles correspond to food supplies up north, where trees often produce heavy seed crops one year, then focus on growth the next. My childhood memory is that grosbeaks were plentiful every year, but that was 50 years ago, and I can’t trust a memory like that when I don’t even recall what I had for breakfast yesterday. Project FeederWatch clearly shows the biennial boom and bust cycle.
The evening grosbeak population is declining across much of its range. Nowhere is the drop more dramatic than it is in the northeastern United States. Numbers have plummeted by 80%. Unfortunately, we collect much of our data in winter when the birds invade southward and mob our feeders. We know surprisingly little about what is happening on the bird’s summer territory, simply because there are few observers and little study in the northern conifer forests. Changes in forestry practices may have changed habitat. Pesticides intended to control spruce budworm may have affected breeding success. Grosbeaks use their heavy bills to crack seeds and cones, but they feed protein-rich larva to their nestlings. Perhaps populations are doing fine up north, and a warming climate is simply making southward invasion less necessary in winter.
On Election Day, the call of the evening grosbeak was welcome. Their screech is one of the most grating bird sounds on the planet, but I miss hearing it.
Bob Duchesne serves as a Maine Audubon trustee and vice president of its Penobscot Valley Chapter. Bob developed the Maine Birding Trail, with information at mainebirdingtrail.com. Bob can be reached at firstname.lastname@example.org.