Rise and fall of evening grosbeaks is mysterious

By Bob Duchesne, Special to the BDN
Posted March 02, 2012, at 8:29 p.m.

Where did all the evening grosbeaks go? When I was a wee lad, flocks of these noisy yellow finches routinely filled my yard. Through the ’80s and early ’90s, they cost me a fortune in sunflower seeds. Even though they were avian vacuum cleaners at my feeder, I cherished them for their gregarious cheerfulness.

Evening grosbeaks resemble huge goldfinches. Males are flashy yellow, black and white. Females are much duller, like female goldfinches. The name grosbeak is derived from the French word “gros-bec,” meaning “big beak.” Although it shares the name with the rose-breasted grosbeak, the two are not closely related. The rose-breasted grosbeak is actually in the cardinal family, while the evening grosbeak is a large finch. It was named the evening grosbeak because it was originally thought to sing mostly at dusk. Wrong. It is raucous all day. And, although I don’t wish to insult its vocal ability, it is difficult to call its screechy chatter “singing.” Sadly, they no longer irrupt from the woods into suburbia in the numbers they once did and nobody really knows why. In fact, there are a lot of things we don’t know about the rise and fall of evening grosbeaks.

It may be that the real mystery is not why they’ve declined in Maine, but rather why they were so numerous at one time. Originally, this was a western bird. It was abundant in the Columbia River Basin in the 1830s, where it was originally studied by early scientists. The first record of a Maine sighting was in 1890. Nineteen years passed before there was another reported sighting. Over time, it became an annual event. Until the 1900s, it was not known to be nesting anywhere east of the Great Lakes. In 1926, the first confirmed breeder in New England was discovered in Vermont. The next nesting pair in Vermont wasn’t noted until 1953. Soon thereafter, it was an abundant feeder bird across northern New England, with populations peaking in the early 1970s. It’s been downhill ever since.

While we may not know the exact reasons for the decline, we can readily measure it. There are citizen science programs that help us assess population changes. For instance, Project Feederwatch is run by the Cornell Lab of Ornithology. All you have to do to participate is look out the window while drinking your morning coffee, which is well within my skill set. Counts sent into Cornell by feeder watchers show puzzling data about evening grosbeaks. Between 1988 and 2006, the number of sites reporting this species declined by 50 percent. Likewise, Christmas Bird Counts showed populations plummeting by as much as 78 percent.

One thing that has complicated the study of grosbeak populations is that the species seems to be a on a 2-year cycle — plentiful one year, scarce the next. Furthermore, even when they wander south in the winter, the locations vary considerably from year to year. We are accustomed to these birds being noisy in the cold months. In summer, they are surprisingly quiet and even stealthy, which is another hurdle to studying them.

The evening grosbeak uses its big bill to open big seeds. It’s strong enough to crack a cherry pit. However, growing babies need protein, so nestlings are routinely fed grubs and larvae. One theory for the decline is that the population rose and fell with the spruce budworm. There are several other northern forest species whose numbers also increased when the budworm and its larvae furnished abundant food.

Other theories attribute the decline to timber harvesting changes in the Canadian forest. Or it could be that a warming climate has reduced their need to come south in winter. Or perhaps the populations have simply stabilized, and the evening grosbeaks have now settled where they should be. After the initial explosion eastward, nature has rebalanced the supply of birds, food and predators and this is the true normal.

We’ve still got plenty here in Maine. During the summer, I can usually find them up in the north

woods. They readily come to the feeders at Historic Pittston Farm on Seboomook Lake. The feeders at Nesowadnehunk Lake Wilderness Campground just outside of Baxter State Park need constant replenishment. I see them inside the park, too. On the Golden Road last summer, two of them landed near me and walked under my parked car. It’s the second time I’ve seen that happen. No, I don’t know why.

Bob Duchesne serves in the Maine Legislature, is president of the Penobscot Valley Chapter of Maine Audubon, created the Maine Birding Trail and is the author of the trail guidebook of the same name. He can be reached at duchesne@midmaine.com.

 

http://bangordailynews.com/2012/03/02/outdoors/rise-and-fall-of-evening-grosbeaks-is-mysterious/ printed on July 30, 2014