November 23, 2024
ON THE WING

Early migrants face cold-weather challenges

A picture can offer much inspiration, as last week’s Bangor Daily News’ front page photo did. A friend of mine saw it before I did and exclaimed, “Well, now you know what to write about in your next column!”

For those of you who didn’t see it, the photo, taken by Robert F. Bukaty, depicted a singing red-winged blackbird. So what, you may be thinking – these images are a dime a dozen.

But this one is truly unique. The sharp-eyed Associated Press photographer caught the action at just the right angle and lighting, with perfect timing, on a cold spring morning last week. So cold, even the air expelled from the bird’s mouth as it sang was visible. The caption read: “With the temperature in the teens, a red-winged blackbird can see its breath as it sings in record-breaking cold weather Friday in Woolwich. Some towns in Maine recorded single-digit temperatures, including Washburn, where it was just 3 degrees.”

Which leads me into this week’s column: What do early spring migrants do when the weather turns against them?

If the weather is severe enough for long enough, they struggle to survive.

Some birds are able to find sustenance by picking over last year’s crop of berries still left on trees and shrubs: sumac, hollies, cedars, and junipers. After our last snowfall, I noticed robins and waxwings gathering in ornamental trees and feasting on the fruit. They also converged on any small patch of exposed lawn, searching for insects, as did the red-winged blackbirds and grackles. The latter will also take seed from feeders or spilled grain in barnyards.

Much depends on the bird’s feeding strategy. Birds such as tree, cliff, and barn swallows, as well as chimney swifts and purple martins, for example, are adapted to taking flying insects on the wing. They will quickly run into trouble if cold weather puts a damper on the insects, according to David M. Bird, professor of wildlife biology and director of the Avian Science and Conservation Centre of McGill University in Quebec.

Writing for the December 2002 issue of “Backyard Bird News,” Bird recounts what happened last spring, when the weather turned cold after these birds had returned to their breeding grounds here in the Northeast.

“In some locales the temperature set new record lows. At temperatures lower than 9 degrees Centigrade (48 degrees Fahrenheit), aerial insects become inactive,” he wrote. “Swallows and martins alike perished quickly, essentially from a combination of hypothermia and starvation – no warmth, no insects, no energy.”

Despite this picture of doom, Bird offered encouraging news: populations of the affected birds rebounded within the same season. This was so, he wrote, because the birds affected were experienced, older birds that had arrived earlier to breed. Younger, nonbreeding birds, called “floaters,” arrived later to fill in the gap – and had their pick of prime nesting sites and the “ensuing post-cold insect bloom.” Many more young of these late breeders, in turn, survived to fledgling age, he wrote.

I would imagine that this scenario is by no means universal for all birds all the time – as someone once told me, “nothing in nature is always so neat and serene.” Now you might be asking: What can I do to mitigate the effects of severe spring weather on early migrants?

Short-term solutions would be to increase the quality of the nesting, feeding, and roosting habitat on your own land. An excellent reference for this is “The Backyard Bird Feeder’s Bible,” by Sally Roth. Other sources, recommended by the Cornell Lab of Ornithology, are “Landscaping for Wildlife,” by Carrol L. Henderson, and “The Bird Garden,” by Steve Kress.

Long-term solutions would involve becoming aware and active regarding conservation issues in and around your community, as well as encouraging responsible, sensible development.

Chris Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com


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