BY RICK BORCHELT

Our unseasonably warm December weather brought the first waves of what will be many robin reports in the local listservs, blogs, Facebook groups and Nextdoor accounts I monitor.
Never mind that the first day of winter, Dec. 21, was only a few weeks ago; one optimistic local gushed that winter was already over because the robins had returned to her yard just before New Year’s Day. Other folks were posting their concerns that robins had been fooled into returning early and might perish in the cold weather yet to come.
All assumed they were seeing the first robins of spring returning from warmer climes where they spend the winter. Throughout much of North America, cabin-fever sufferers rejoice in robins as harbingers of spring.
Usually, they’re wrong. Robins have been here all along.
American robins (Turdus migratorius) are, as their name implies, sometimes migratory. Except when they aren’t.
Even as the robin is a well-known, iconic bird, we actually understood very little about their migratory habits until recently. A Georgetown University graduate student, Emily Williams, is working out the surprisingly complex movements of robins across the American landscape.
Williams has tracked robins from origins as far-flung as Alaska, Texas, Massachusetts, South Carolina — and D.C.

“They’re a truly cosmopolitan bird,” she told Audubon Magazine in 2020. “They may be the most widespread songbird in North America, and yet there’s so much we don’t know about them.”
Williams has determined that American robins are, for most of us in the East, with us all year long, even up into snowy New England. It’s just they may not always be the same robins. Only in extreme northern climates do they quit the neighborhood completely and migrate south.
Williams and her colleagues tracked four robins captured in Alaska’s Denali National Park and Preserve to overwintering sites in Texas, Nebraska, Oklahoma and Montana, up to almost 3,000 miles from the capture location. One robin captured in Amherst, Ma., overwintered in South Carolina, 750 miles from the capture location, while two robins captured in D.C. had spent the entire year right here in the suburbs.
So, Williams notes, American robins may be as varied in their provenance as the rest of D.C.’s residents. Some robins were born and bred here and never leave, while some come from far away and soon leave again for better opportunities. Flocks in our area usually consist of both local and migrant robins.

If you’ve noticed more and more robins during winter, though, your eyes are not deceiving you. Every winter, the Cornell Lab of Ornithology organizes a citizen science project called Project FeederWatch, where people report sightings of birds in their yards over two consecutive days between November and April. For the past 25 years, FeederWatch data has shown that more American robins are hanging around farther north than they used to, and they’re arriving earlier, even in the northernmost parts of their range.
Robins may be responding, in part, to the warmer winters brought by climate change, but odds-on betting is that there are also more food resources now available for them through the winter. While we may think of American robins as the proverbial early bird getting the worm (and other invertebrates), their entire metabolism undergoes a radical makeover in winter from carnivory (that worm!) to frugivory, or fruit-feeding.
Their favored winter sustenance in the Mid-Atlantic is the small fruit of the now-ubiquitous invasive Callery pear (Pyrus calleryana), also known as Bradford pear. American holly, winterberry, hawthorn and crabapple berries are also at the top of the robin’s cold-weather menu.
Their social behavior also switches up, from pairs or small family groups in summer to large, roving winter flocks of hundreds of birds that may fly long distances for the best fruit options. This means they’re mostly absent from lawns and gardens when it’s cold, favoring instead woods and forests with better berry crops. So while the robins are around, they just aren’t very visible to most of us — or very vocal.

Courtesy of Mason Maron/Macaulay Library
When the weather warms up and the ground thaws completely, American robins will switch back to a diet of mostly worms, caterpillars and grubs. And they’ll become feisty defenders of backyard territories, with frequent clashes between males as they work out family boundaries. Males also take up their insistent song again in spring, often singing through the night at the height of the mating season.
There’s a possible human health downside to all those robins running around, according to Indiana University researcher Alex Jahn. He and his colleagues have discovered that robins can transport Lyme disease far across the United States by hosting both the infectious bacteria that cause Lyme and the ticks that then carry it.
You can listen to a podcast about robin migration with Emily Williams, sponsored by the American Birding Association, at tinyurl.com/5xkfjkmp.
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Have questions for Rick about the world of nature in and around the Maryland suburbs or suggestions for future columns? Drop him a note at rborchelt@gmail.com.