Foraging Pine Warbler
Foraging Pine Warbler
Throughout a fortnight of extended cold snap, Mainers endured sub-zero temperatures, howling winds and blowing snow. “It’s January in Maine,” we tell ourselves. We stayed indoors when possible and dressed snugly when venturing outside. For those bold winter folks who spend time outdoors in such conditions, a gradual physical adaptation process comes to pass: a physiological acclimation to the cold, an acquired sensation of “getting used to it.” That’s why sudden rises in temperature toward the freezing point feel relatively warm to us.

Let’s consider the Siberian Huskie as an example of physical adaptations to extreme cold conditions. Able to withstand -60°F temperatures, Huskies have a double coat of thick insulating fur and compact, triangular ears, fur-lined like natural ear muffs to resist frostbite. Their long, bushy tail is able to reach their face and curl around their nose while they’re sleeping. Almond-shaped eyes reduce the need to squint on snow-glared landscapes. This breed is truly acclimated to colder climates. But even Huskies require weather-secure housing (often lined with dry hay) to survive brutal Arctic overnights. A domestic pet Huskie from these parts would not withstand such frigid conditions, however, if transplanted into that hostile environment.

Most birds currently wintering in Maine are well adapted for harsh weather conditions. With temperatures of -13°F, I recently witnessed a mixed group of Mallard Ducks and gulls loitering on a windswept ocean shoreline. From the sanctum of my heated car, the birds appeared impervious to the blinding cold. With heads tucked for warmth, a portion of them reclined in a flowing freshwater brook, with bellies and feet submerged in the partially frozen water. Under these challenging conditions, how could the birds bear the water? Gulls and ducks have robust circulatory systems that pulse heated blood throughout their legs and webbed feet. We might also realize that the temperature of the trickling brook was possibly 40 degrees warmer than the surrounding layer of smoky sea air.

Now that songbirds have finally noticed our feeders, we can study their social interactions and unique winter survival tactics. Stepping outside to fill the feeders one morning, I was surrounded by a trio of wing-flicking, chittering Golden-Crowned Kinglets as they explored the outer limbs of a maple. Kinglets are even smaller than chickadees! Despite their tiny size, kinglets inhabit Maine spruce forests year-round, subsisting on a winter diet of microscopic insect larvae. At night, chickadees and kinglets enter a state of self-induced hypothermia that preserves life-sustaining heat stores until the following morning meal.

Several of my other feeder regulars — goldfinches, jays, starlings and Mourning Doves — use other tactics to cut heat losses, lowering themselves directly against the ground during feeding. Since the majority of body heat is lost through the bare bill and leg surfaces, any means of shielding exposed anatomy pays dividends. The tender toes of Mourning Doves, a species with historic southern origins, are occasionally subject to frostbite.

One appealing aspect of feeding birds is the possibility of attracting unusual or out-of-season species. Glancing at several goldfinches out my picture window, I noted a slightly different looking bird in the feeder tray last week. It was a Pine Warbler! This relatively large warbler species occasionally lingers in winter, mostly at feeders. It is less energetic than the finches, and I noticed the greenish-olive warbler’s yellow throat, white wing-bars and rather longish tail.

Dropping down to feed on the ground, the warbler eventually settled into a prone position, protecting its feet from the early-morning cold. At first I was concerned by its sluggish behavior but, as the morning progressed, the bird grew perkier — even animated enough to start bobbing its tail!