Nome’s winter birds and how they survive— Part 1

Recently, it was -12°F at Banner Creek in the dim light of late morning. Out the window, three chickadees flitted and bounced energetically through the willows, eating and caching seeds from our feeder. A little later, out another window, a dipper popped in and out of a small open hole in the Nome River, from frigid water into even colder air, perching briefly on the ice edge.
It seems miraculous that these and other small birds manage to survive and thrive in the harsh winter conditions that most birds have escaped by flying south, months ago. So, who are these few hardy winter residents that we will be hoping to find on the Christmas bird count? And how do they manage to find food and stay warm through the rigors of subarctic winter?
For most of the 49-year history of Nome’s Christmas Bird Count, observers have found the few predictable species that regularly winter in taiga and tundra regions of the north.
Ravens are seen most often, followed by McKay’s and snow buntings; willow and, less often, rock ptarmigan; black-capped chickadees; American dippers; redpolls; gyrfalcons; northern shrikes; downy woodpeckers; pine grosbeaks and Canada jays. Infrequent sightings of unexpected passerines or an owl species occasionally add spice.
Also, in recent years, late freeze-ups have often allowed volunteers to spot lingering seabirds from shore, including common, king and spectacled eiders, glaucous gulls and long-tailed ducks. These hardy seabirds regularly winter along the ice edge in the Bering Sea.
The focus of this article is our few overwintering land birds and some intriguing adaptations and behaviors that enable them to eke out a year-round living in the frozen north.
Staying warm and finding food are key to a bird’s winter survival. Preparation for a northern winter begins in late summer and fall when birds ramp up their food intake to gain weight and increase their fat reserves. Fat provides insulation and a store of energy to burn during cold nights, storms or periods of food scarcity.
Feathers are the next line of defense against the cold, and northern birds put on heavier coats of plumage for winter. The soft, fluffy down feathers next to a bird’s body are as effective as any known insulation. Using muscles at the base of their feathers, a bird can raise its feathers to fluff them up. This creates tiny air pockets that trap heat, increasing the layer of insulation around the bird.
Using oil from a gland at the base of their tails, birds fastidiously preen their feathers to clean and waterproof them. The outer feathers provide a weatherproof shell that keeps the bird warm and dry and retains body heat by keeping out cold air.
Feathers insulate the bird’s body, but bills and most legs and feet are bare. To prevent excessive heat loss, those features tend to be smaller in species that overwinter in cold climates.
To reduce heat loss from these exposed appendages, birds will tuck their bills into feathers on the top of a wing when roosting, which also enables them to breathe warm air. They may crouch to cover their bare legs and feet with fluffed feathers, and some will perch on one leg to tuck and warm the other.
Ptarmigan have feathers on their feet, which become denser and downier in winter. These feathers provide insulation and increase the surface area of their feet, effectively creating snowshoes. Gyrfalcons have dense feathers on their thighs that drape down to cover and insulate much of their lower legs, keeping their leg muscles warm for the hunt.
Most of our winter birds lack this protection, and who hasn’t marveled at a bird’s ability to endure cold, bare feet! And they do get cold, but apparently not uncomfortably so. 
Birds have the ability to keep their bare feet and legs just above freezing while their body temperature stays around 105°F. Blood flows to and from the feet through a heat exchange network of blood vessels. Warm arterial blood heading from the heart to the feet, flows next to incoming cold venous blood flowing up from the feet. Blood moving toward the heart is warmed while blood flowing toward the feet is cooled. Thus, little energy is spent warming the bare extremities, and loss of body heat is minimized.
Still, feathers and blood flow only go so far to keep a bird warm through a Nome winter. A bird still needs a sheltered place to hunker down for the night and ride out stormy weather.
Chickadees and downy woodpeckers cram themselves into tree cavities which they find or create themselves, or occupy other cozy nooks and crannies, sometimes in man-made structures.
Ptarmigan, buntings, and redpolls all roost in the snow, sheltered from wind by drifts or vegetation. In extreme cold or stormy weather, they dig snow shelters where they overnight or weather a storm.
Northern shrikes, Canada jays and pine grosbeaks roost in the protective depths of dense vegetation, especially in conifers, if available. Pairs of jays and flocks of grosbeaks may huddle together with their own kind for warmth, while shrikes are solitary.
Ravens spend cold winter nights in large communal flocks, roosting together for warmth in secluded, naturally protected areas, or sometimes in abandoned structures. In the past, abandoned dredges have sometimes been the roosting site for hundreds of Nome’s ravens that could be seen streaming in and out at dawn and dusk.
American dippers roost along stream banks, under willow boughs or ice shelves, close to the open holes in the ice where they feed. There, the relative warmth of the flowing water creates a comfortable microclimate for a densely feathered dipper.
Inside their shelters of choice, birds can shiver on demand to generate body heat until it is time to emerge, feed and replenish their reserves. If you have a bird feeder, you may have noticed that it is especially busy at first and last light. Birds have an urgent need to refuel in the morning and stock up for the night.
Birds also feed voraciously before storms so they are prepared to hunker down out of the wind and weather for up to a day or two, living off the extra food they consumed.
A follow-up article in January will delve into various foods and feeding behaviors our resident birds rely on in winter, and unique physiological adaptations that some of these species have developed for winter survival in the north.