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Some Upper Peninsula species depend on snow

Northwoods Notebook

(Betsy Bloom/Daily News photos) A male pine grosbeak feeds on crabapples in northern Dickinson County. This has been a good “irruption” year for the large finch, an on-and-off visitor to the region.

The region did manage to have a white Christmas, though the cover was relatively thin and wind-swept.

While supposedly a La Nina year — which, according to NOAA, tends to create “snowier-than-average conditions across much of the northern U.S.” — the snow has been scant so far this winter, at least in our part of the Upper Peninsula, though the western side this week got more than a foot from the storm system that swept through the Dakotas and Minnesota.

It’s been more typical of what the southern states normally see from La Nina in being warmer and drier than normal.

The effect on the human population is mixed but minimal — better for driving, poor for winter outdoor activities such as skiing and snowmobiling.

Little snow can be a boon for deer that don’t have to dig for forage, much less expend energy wading through drifts.

Ruffed grouse develop new bristles on their feet in winter — better for gripping branches and maneuvering in snow.

But for a number of local species, too little snow can be as much a hardship as too much.

Snowshoe hares and the three weasel species — long-tailed, short-tailed or ermine, and least — have little choice on turning white with the season. The change is triggered by the shortening days and, for the hares, brings a denser gray undercoat to better cope with colder conditions.

If the snow is late in showing up, these white figures become easy to spot. That can be a lethal vulnerability for the hare — already on every predator’s menu — and weasel, small enough to be snatched up by hawks and owls.

A winter with little to no snow can hamper the weasel’s ability to hunt as well, since it makes them more conspicuous to prey. Weasels have lean bodies designed to fit in tight spaces and high metabolisms that experts say requires consuming a third or more of their body weight a day. That leaves them constantly hungry, with little in reserve to draw on, so they must feed regularly or can quickly starve.

With snow now on the ground and more in the forecast, it’s likely these white creatures are back to blending in.

But they and others could use some real snow depth, not just paltry flurries, to take full advantage of their adaptations to winter life in the North Woods.

The snowshoe hare’s signature back feet allows it to skip across the snow surface while a pursuing predator bogs down. Mice and voles can establish tunnels that keep them concealed or at least tougher to locate.

Ruffed grouse like to plunge into snow drifts as shelter for the night, where their body heat will turn the cavity into a snug burrow. Grouse in winter also develop new bristles on their feet that are thought to help them in walking across snow, as well as getting a grip on branches while feeding on tree buds.

Losing these advantages can make a difference in surviving the rigors of winter — so let it snow, let it snow, let it snow.

*****

The results for the Christmas Bird Count in Dickinson County aren’t all yet in — participants have until Jan. 4 to submit their lists and tallies — but at least one of the hoped-for winter finches did make an appearance, coordinator Phyllis Carlson said: pine grosbeaks, not uncommon in the region but not reliable, depending on the year. This has been a good “irruption” year for this large finch, to the point that two already have been brought to another local wildlife rehabilitator.

Best way to spot pine grosbeaks is by looking for birds flying into or hopping around fruit-bearing trees such as crabapples; Carlson saw some in trees just outside the entrance to White Birch Village on U.S. 2. Pine grosbeaks tend to be in flocks, too, so it’s more likely to encounter many than one.

I’ll share what else was seen during the count when full results are available.

Betsy Bloom can be reached at 906-774-2772, ext. 240, or bbloom@ironmountaindailynews.com.

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