If you’re a white-footed mouse, 2 feet of snow might be a welcome forecast, but if you’re a black-capped chickadee or a white-tailed deer, it’s bad, bad news.
The bitter cold, deep snow and, now, rain and warmth are for birds and animals extremes in the battle for survival, from which some emerge in spring as winners. Others lose.
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It’s nature’s way of keeping things in balance and ensuring that the strong survive, wildlife biologists and rehabilitators say.
“The strategies are really diverse,” said Mike Windsor, of Maine Audubon Society in Falmouth.
The first and most obvious is the one humans often embrace.
“A lot of animals are really just hunkering down,” waiting for the worst to blow over, said Windsor. In this recent round of exreme weather, “a lot of factors (were) coming together,” he said. That meant animals had to use “multiple strategies” to get through.
The birds seemed to sense the storm even before it started. Windsor noticed an “uptick in activity the night before” at the feeders in his own backyard. Eating more seed than they ordinarily would packs on a little extra weight — not a bad plan just before a heavy snow. Then, when the bluster starts, they can sit tight and wait things out.
And the snow is just the kind of insulating blanket some creatures need to flourish, said Judy Camuso, wildlife biologist with the state Department of Inland Fisheries and Wildlife. Birds like ruffed grouse “burrow in the snow” for insulation, she said.
Some animals — mice, voles, moles, shrews — “do better with snow cover,” she said. It gives them a safer way to move around — in tunnels — that insulate them from turbulence and trouble up above.
Having that protection makes it harder for owls to prey on tunneling mammals, but only in the short term. Avoiding raptors now may produce “a really good rodent population come spring,” an apparent boost for the small mammals. But that, in turn, becomes a boon to owls, fox and fishers who all feast on the small rodents and other mammals, she said.
The larger mammals “do very well,” Camuso said, “provided they survive the winter.”
And as hard as these conditions might seem, native birds and animals “are pretty well adapted for this,” said Kristen Lamb, director for education and outreach at The Wildlife Center in Cape Neddick, which helps rescue and rehabilitate injured and orphaned animals.
But this weather is not for the inexperienced.
Juvenile owls and hawks make up most of the number of vulnerable creatures that have been hurt, Lamb said. In January alone, the center got 12 raptors, “all hit by cars,” she said.
Encounters with humans rather than brutal weather often end up placing some animals at risk. The snow and cold are challenge enough, said Lamb, but “when you add fish hooks, cats and cars on top of that,” it’s harder for already stressed birds and animals to survive.
Then again, not all of the human impact is negative.
Some man-made “corridors,” such as plowed driveways or snow tamped down by skis, snowmobiles and snowshoes, make movement a lot easier for deer and other large mammals, said Lamb’s colleague, Sonja Ahlberg, a wildlife specialist at the center.
For birds, feeders are “an added boost” among seed eaters, though species that thrive on insects are out of luck right now, she said. Birds like juncos and goldfinches are helped by people who heap on the seed because “songbirds have to eat all the time” to make it through the cold months.
Goldfinches clung to the feeder at Ahlberg’s house in Cape Neddick right through the worst of the blizzard last Friday and Saturday, she said. “They didn’t move the entire time.”
Many species of birds including the black-capped chickadee use daily torpor to get through especially longer-term stretches of freezing weather, Lamb said. Daily torpor is like low-grade, short-term hibernation: The metabolism slows for a few hours, using less energy, lowering body temperature just a few degrees and saving “a significant number of calories from being burned off overnight.”
Certain birds, including robins and eastern bluebirds, face “additional hardships,” if they stay this far north, at the margin of their range, Lamb said. The somewhat balmy winter of December and early January lulled some into lingering too long, and now in bitter February, they’re “trying to make it” in conditions wetter and colder than they’d prefer.
Ordinarily, the birds’ plumage provides adequate protection from the elements, Ahlberg said, but the snow-turned-to-rain, combined with the “wind ruffling their feathers … makes them more prone to hypothermia.”
Still, winter dieoff — the loss of a certain percentage of a species — is normal, Lamb said, and it actually prevents starvation and disease, because weaker individuals perish and the stronger flourish, in part because there is less competition for food.
The population becomes “sustainable and strong” as a result of the less vigorous members being culled by the cold.
Deep snow can be a challenge for the cloven-hooved white-tailed deer, which are heavy enough to pierce through snowdrift and banks.
“It will restrict their movements,” Camuso said.
Then, if the temperatures warm temporarily and the snow melts a little — or it rains, as it has this week — and is followed by a hard freeze, it can be rough going, not to mention tough on the slender legs of deer scraping through a surface that feels like shattered glass.
And “if that top layer is a few inches thick,” it affects a whole range of creatures.
For example, she said, an owl “can’t get through” to capture prey, she said.
Winter is “a big season for us to get (injured or sickly) porcupines,” said Ahlberg.
These prickly slowpokes are “prone to get skin infections” and mange in the colder months, she explained, though not enough research has been done to explain exactly why.
Staff Writer North Cairn 791-6325
ncairn@mainetoday.com
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