by Anna Morris
QUECHEE — One January day, my husband and I set off on a walk around our neighborhood. The temperature was a bone-chilling negative 19 degrees, and although we worked to get our blood pumping, our fingers and toes eventually revolted. As we turned back toward the warmth of home, I spotted a flock of birds bouncing through the branches of a sumac. When I looked more closely, I was shocked to see that the birds were American robins.
What were these heralds of springtime doing in our woods in January? These robins would be neither late migrators nor early arrivals at this time of year. I wondered how unusual it was to see American robins in winter in New England, and how this dozen or so were getting by while their usual earthworm fare was burrowed deep in the ground and buried beneath a foot of snow.
Most people know American robins as migratory. After all, their scientific name is Turdus migratorius: the migratory thrush. (A fun fact to impress your bird-nerdiest friend: American robins are actually thrushes, not robins, a group only found in Europe and Asia.) We are used to saying goodbye to their red breasts and varied vocalizations by early November, and welcoming them back with warming temperatures in late March.
Many of our summer bird species are “complete” migrants, meaning they vacate northern latitudes as a species in autumn and spend the winter much farther south. American robins are “partial” migrants. Some, hungry for worms and insect larvae, do fly short distances south during the coldest months. Others, however, stay put and switch up their menu for the winter to suit their location.
It is not uncommon to see flocks of up to 50 American robins descend on a snow-dusted berry bush, even on the coldest winter days. The robins’ downy feather undercoats help keep them warm, but only if the birds have fuel to burn. Although berries do not provide as much crude protein as insects do, they make up for this with high amounts of sugar and fat. Native, fruit-bearing trees and shrubs provide the best food for robins in winter. In New England, these include staghorn sumac, downy serviceberry, American cranberry, red chokeberry, winterberry, and eastern red cedar. Robins may also visit winter bird feeders if mealworms, waxworms, cranberries or other berries are part of the mix.
Anyone who has watched two male robins vie for the right to display their russet-red chests on the same patch of lawn knows that they are not exactly tolerant birds. But the infrequency of berry bushes, paired with the density of berries on each plant, means that the robins must learn to share, and so their winter behavior changes along with their diet. This temporary truce may also help American robins keep warm, as they gather with a few fellows in tree roosts at night, conserving body heat. Their fluffed feathers trap heat, and a countercurrent exchange system in their legs helps retain warmth, even though their feet are bare to the icy temperatures.
Even with these adaptations, the movements of American robins in winter are changing alongside our climate. According to data collected by community scientists — through projects such as the National Audubon’s Christmas Bird Count, now in its 123rd year, and Project FeederWatch, run by the Cornell Lab of Ornithology — American robins are becoming increasingly common during winter in the Northeast. Thirty years ago, American robins were completely absent from censuses of backyard bird feeders in Vermont and New Hampshire in January. Last winter, 10 percent of feeders had a robin visitor in the same time period. In fact, American robins have now been documented in the month of January in every U.S. state except Hawaii (where they don’t occur at all), and every Canadian province except Nunavut.
We can be good neighbors to overwintering songbirds by planting native, fruit-bearing plants such as the ones listed above. You might even plan ahead for spring by consulting The Audubon Society’s Native Plant Database (audubon.org/native-plants), and keep in mind that native plants are important for pollinators, too. When I see robins in winter now, I remind myself that these versatile thrushes of all seasons are common for a reason: just like us, they know how to weather the winter.
[Anna Morris is an environmental educator at the Vermont Institute of Natural Science. Illustration by Adelaide Murphy Tyrol.