Birders excited by invaders from the north

Posted Dec. 16, 2011, at 1:33 p.m.
White-winged crossbills are highly irruptive, wandering south into Maine even in summer, where they may nest in a good cone year.
Courtesy of Bob Duchesne
White-winged crossbills are highly irruptive, wandering south into Maine even in summer, where they may nest in a good cone year.

As you read this, we are being invaded. Devious birds are sneaking across our defenseless borders. They are Canadian birds heading south for the winter, and we’re the south. Many of these birds gather in predictable numbers in predictable places each winter. But some are just plain unpredictable.

In birding terms, they are called winter irruptives. The words “erupt” and “irrupt” come from the same Latin root and mean roughly “exploding forth.” One particular definition of irrupt relates to the sudden upsurge in natural populations, especially when ecological balances and checks are disturbed. That’s exactly what happens when food shortages or frigid weather drives birds south. Irruptive owls were discussed last week, but there are plenty of other northern breeders on the list, including birds that eat seeds.

White-winged and red crossbills are highly irruptive, wandering south into Maine even in summer, where they may nest in a good cone year. Both species are widespread breeders across Canada, but the red crossbill tends to wander a little farther south in the western states.

Visiting birders appreciate that the harder-to-see white-winged crossbill is actually a little more common in Maine. As their name implies, the tips of their bills cross, almost like scissors. This adaptation allows them to twist the seeds off cones. They have a preference for spruce, but aren’t averse to hemlocks and pines.

Overall, crossbills were pretty scarce last winter, having devoured many of the cones over several previous winters. We’ve got a pretty good cone crop this year, and I’ve been seeing both species since August, so I’m expecting a good winter for them.

Once you get used to them, crossbills are pretty easy to locate because they are noisy. Like most finches, they find safety in numbers and join foraging flocks, wandering in search of food for considerable distances. That requires them to communicate constantly with each other so that they can stay together.

When flying or sitting, their jip-jip-jip calls are easily heard. Near Bangor, the area around Sunkhaze Meadows National Wildlife Refuge in Milford is good, including the entire length of the nearby Stud Mill Road. The coast from Acadia to Quoddy Head usually has crossbills in the maritime spruce and fir forests. The Golden Road west of Millinocket produces large flocks and it’s fun to go there in the winter. The Long Falls Dam Road in Lexington Township, on the back side of Bigelow Mountain and Flagstaff Lake, is another favorite place of mine.

If you’re having trouble, try this tip: Intersections on snow covered roads are frequently churned up into a mixture of snow and gravel. Crossbills and other finches congregate around such places because they ingest the gravel to help with digestion.

Smaller finches also irrupt. The pine siskin is a Maine breeder in the northern forest, but it wanders widely in winter, visiting feeders often. The siskin is similar in appearance to its close cousin, the American goldfinch, though it is a streaky brown with a bit of yellow in the wings. They are similar in habit and will join foraging flocks of goldfinches.

In fact, I’ve been watching them flock together for the last month. On a pre-Thanksgiving trip to Moosehead Lake, they were everywhere. Common redpolls are not Maine breeders. They nest in the subarctic and are less predictable. When they irrupt, the numbers are large. It’s not unusual to see a hundred of them mobbing a thistle feeder and the ground below it. They were mostly absent last year, but I have high hopes for this winter.

Three birds of open country irrupt into Maine. Snow buntings are members of the longspur family and can be abundant on hayfields and blueberry barrens. They also frequent ocean edges where high tides have cleared the snow, especially in dune areas.

The Lapland longspur is related and shares the same arctic breeding ground with the snow buntings, often traveling with them.

The horned lark is not related to the longspurs. It is the only true member of the lark family in North America and is a widespread breeder in the U.S. Since they also like open fields, flocks of buntings can contain a few larks in winter.

So what is the last of the three groups of irruptive species? I’m afraid, like Christmas, you’ll have unwrap that present next week.

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.

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