Although typically desert dwellers, roadrunners may also thrive in cold climates by fluffing feathers for insulation and by exposing their black back feathers to the sun.
A dark-eyed junco feeds on weed seeds on a crisp winter day.
Cindy Murray
Although typically desert dwellers, roadrunners may also thrive in cold climates by fluffing feathers for insulation and by exposing their black back feathers to the sun.
Have you ever wondered why certain Northern Arizona bird species remain here year-round while others fly south to warmer environments? On any clear, frigid winter’s day, we spy house finches, dark-eyed juncos, woodpeckers, corvids, crossbills, and jays busily foraging in our forests, backyards, and around shopping centers. Are these birds somehow physically or behaviorally adapted to withstand cold? How do cardinals withstand extreme heat in the desert but also thrive in cold climates, and why don’t we have them in Flagstaff?”
First, let’s examine why many birds fly south in the fall and remain there through winter. Because it takes more energy (calories) for any bird species to survive in cold climates, the question of whether one migrates or remains in its breeding habitat is a matter of food availability and caloric density. Birds with short, flat beaks, like swallows, swifts, and nighthawks, are adept at nabbing insects in mid-air. But in northern or high-elevation climates like ours, few insects are active during winter — most, depending on the species, overwinter as eggs, pupae, or adults tucked away under bark, underground, or in natural or man-made crevices. Hence, insect-nabbing birds fly south or to low elevations. Waterfowl migrate before their aquatic food sources freeze. And warblers, with their small, sharp beaks intended for gleaning small arthropods from leaves and twigs, usually migrate.
Certain species including grosbeaks, sparrows, finches, and cardinals have cone-shaped beaks designed to feed on energy-packed foods, namely nuts and seeds. And because many cold-climate regions are rich in these foods, these birds don’t migrate. Crossbills have a curiously unique adaptation — a large bill crossing at the tip, affording great strength capable of extracting seeds from cones.
All western jays have multi-purpose, heavy bills and don’t migrate. Pinyon jays remain in or near their southwestern pinyon pine/juniper habitats year-round. With long, strong pointed beaks, they are adept at finding and caching pinyon nuts, insects, and other foodstuffs in the fall. Remarkably, they nest in winter, feeding on their cached food. They all stay within a small circumference, with one bird family to a tree. The flock will choose an alternate winter habitat when pinyon pines fail to produce cones, but they rarely travel far.
Nuthatches, sporting long, pointed beaks, and chickadees, bearing short, pointed beaks are also omnivorous. They glean diapausing insects, insect eggs, and immature insects from trees, and may also gorge on seeds in winter. They too, cache food in the fall.
Certain species like robins switch their diets from worms and arthropods to berries and seeds but will migrate, when necessary, especially far-northern birds. Other behavioral winter traits include huddling together to share each-other’s heat, tucking one foot into their downy feathers, and hunkering down as stormy weather approaches.
We’ve all seen tranquil Christmas cards depicting puffed-up cardinals in a snowy scene. Fluffing feathers is a survival skill that creates multiple air pockets, trapping heat inside a blanket of insulation. Feathers are remarkably water-resistant. Additionally, many winter birds shiver, generating heat, by tensing their muscles. In times of extreme cold, some birds like cardinals may allow their body temperatures to drop by 3° to 6°F.
So, why don’t cardinals inhabit Flagstaff? Cardinals seem to find plentiful food sources year-round in Arizona’s desert environments, including bird feeders. I believe they simply haven’t had a need to expand their territory. But then again, who knows?
Winter survival strategies often require a great expense of energy, but birds have an ingenious adaptation limiting this loss — their feet! Because a bird’s foot consists of mostly tendons and bones, but scant fluids, it doesn’t become frostbitten. As All About Birds from The Cornell Lab explains, “Birds… have a countercurrent heat exchange system in their legs and feet — the blood vessels going to and from the feet are very close together, so blood flowing back to the body is warmed by blood flowing to the feet.” This way, less energy is expended in reheating blood as it reenters the body. Songbirds have yet another winter energy-conserving tactic: putting on an extra layer of fat.
Finally, but importantly, birds of many feathers weather winter together: a hodgepodge of species frequently bands together. Irrefutably, many pairs of eyes and ears serve better than just one to find the food sources required for winter survival.
Don’t miss the Community Seed Swap at the East Flagstaff Community Library on March 24 from 2 to 4 p.m. Bring some seeds, swap some seeds, and meet other gardeners. You don’t need to bring seeds to participate.
Cindy Murray is a biologist and co-editor of Gardening Etcetera and has been a Coconino Master Gardener since 2010. She is married and has two amazing grown children and two grown grandchildren. Cindy enjoys photographing Arizona’s great outdoors, especially sunsets, birds, and insects. She is a member of Arbor Day Foundation, Audubon Society, The Nature Conservancy, and The Cornell Lab of Ornithology.
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