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Spring peepers call; migrating birds are on the clock to nest

Northwoods Notebook

Tree swallows soar near a nesting box in northern Dickinson County. (Betsy Bloom/Daily News photo)

When the weather finally grants the region a few real warm days, the birds that have returned to the Upper Peninsula recognize their cue.

As the dawn arrives just a little bit earlier each day, the morning becomes a chorus of interweaving avian songs.

But when the day draws to a close, one call dominates them all, from an unlikely amphibian source: the spring peeper.

These diminutive frogs with a voice turned up to 11 are among the earliest of cold-blooded creatures to emerge each spring, filling the forest with the one-note chirping call that give the species its name.

The lakes can still have ice and the forests lingering snow when peepers rouse themselves and begin announcing their presence with authority.

They have a few unique gifts that allow them to be the first frogs in the pond, even before winter is willing to make a final exit, said James Harding, an instructor and herpetology specialist with the Department of Integrative Biology at Michigan State University.

First, they have a natural antifreeze that protects their innards from fully freezing, which allows them to remain fairly close to the surface when digging down into the soil for winter hibernation — they might go only a few inches below the leaf litter, Harding said. For comparison, American toads need to burrow deep enough to avoid the frost line so they don’t risk a fatal freeze.

They also can dehydrate critical organs to, again, guard against having damaging ice crystals form in soft tissues, Harding said.

And unlike other animals that come out of hibernation thin and hungry, spring peepers don’t need to feed immediately but usually have enough stored energy to focus their attention on finding a mate and moving down to the water to get an egg mass going, Harding said.

That means they don’t have to time their emergence to insects being available.

Should the weather regress and the pond or lake where they choose to lay get chilled enough to ice over again, no problem — those eggs can survive a little ice so long as they maintain contact with the surrounding water and are not completely encased, Harding said.

The adults, too, can withstand a cold snap by staying in the water until the weather turns again. While a warm-blooded robin struggles if a late snow persists — its metabolism is such it can starve within days if blocked off from food — the frog can become inactive and wait it out.

“They’re tough little critters,” he said of the peepers.

But what is gained by being out so early? It lets the tiny peepers get a literal jump on breeding, with perhaps fewer hazards and certainly few other frogs. Only the wood frog has a similar ability to withstand freezing while hibernating just below the forest floor, so it can emerge while spring is still young.

By the time the much larger toads, gray tree frogs and green frogs are out in force, the peepers will be done, go silent and relax for the rest of the summer.

Incredibly, they’re not the only amphibians to take this route in the North Woods, Harding said. Blue-spotted and red-backed salamanders sometimes can be found crawling across snow, headed for small, temporary meltwater ponds without fish to deposit their eggs where they won’t be eaten, Harding said.

The abilities of animals seemingly ill-suited for such climates to adapt to the conditions of the far north never ceases to amaze.

*****

The warmth of last weekend and mid-week proved enough to clear the last of the ice from Six Mile Lake, though not before winds shoved what was left down to our end, temporarily eliminating the open water along the shore that had allowed for a daily parade of waterfowl, some of them coming onto the lawn to forage under the bird feeders. The crowds on some days resembled a Disney film, with ducks and geese mingling with deer, squirrels, chipmunks and rabbits.

New spring arrivals include belted kingfishers, white-throated and chipping sparrows, and tree swallows testing out the nesting boxes set up on fenceposts on a nearby property that has an open field. Female red-winged blackbirds have caught up with the males.

The first common loon I’ve seen — or heard — checked in Thursday. And a pair of green-winged teal — the little males are among the flashiest of ducks, almost rivaling the wood duck — loafed and preened alongside mallards on a patch of floating vegetation.

I watch every shape on the now-open lake in hope of a horned or eared grebe, far more colorful than the more common pied-billed grebes and both species sporting fancy feathered headgear.

This week’s cooldown might put a bit of a damper on the movement north, but most that have started the journey now are on the clock to get breeding sites established. It would not be a surprise in the next week to hear the first orioles and rose-breasted grosbeaks have been sighted.

Betsy Bloom can be reached at 906-774-2772, ext. 40, or bbloom@ironmountaindailynews.com.

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