Stay, little cheerful Robin! stay,
And at my easement sing,
Though it should prove a farewell lay
And this our parting spring. . . .
Then, little Bird, this boon confer,
Come, and my requiem sing,
Nor fail to be the harbinger
Of everlasting spring.
— Williams Wordsworth, “To a Redbreast (In Sickness)”
When I was growing up in the suburbs of Fairfax County, the first appearance of robins each year was considered a sign that spring was on its way. The American robin (Turdus migratorius), the largest North American thrush, wasn’t generally seen until at least the middle of February and was considered a seasonal migrant; so much so that its scientific name, migratorius, comes from the Latin word for migrating.
In the past few years, I’ve noticed more individual robins in the winter. However, until a flock of at least a few dozen suddenly showed up in the forest edge across from my house early in January, I never tried to find out why more seemed to be wintering here lately. According to a Feb. 14, 2013, article on the WTOP website, I’m not alone in observing the uptick in this species here in the winter: “Many locals have been noticing more backyard American robins during the cold winter months.”
The National Audubon Society oversees Christmas bird counts that started in the early 1900s and now number 2,200 globally. Geoff LeBaron, who since 1987 has been in charge of counts, is quoted in the WTOP article as confirming this trend:
“Historically most of the robins wintered pretty much in the deep south/southeastern U.S. Over the last 40 to 50 years they’ve increased significantly, especially in the northern and eastern part of their range.”
With worms and insects rarely available this time of year, robins rely on fruits instead, according to All About Birds. As winter approaches and the ground starts to freeze, robins move to moist woods, where berry-producing trees and shrubs are common. The site goes on to say that, during the winter, robin roosts “can be huge, sometimes including a quarter-million birds.” Because robins spend less time in yards this time of year, people living in the cities and suburbs are less likely to see them.
Many bird species, including robins, either stay in one place year-round or in the winter go where it’s warmer and food sources more plentiful — south or to lower elevations. Robins are hardy birds and easily adjust to changes in climate by shifting their wintering and breeding grounds as needed to find food. That means those in the flock I’ve been seeing at my house could have spent their summer in New England or Canada. The winter flocks break up as spring approaches, with individuals go off to stake out nesting territory.
The two most common explanations I found for robins wintering farther north, including from LeBaron, are warming temperatures (last year being the hottest on record globally — see sidebar) and nonnative plants introduced for ornamental gardening, especially honeysuckle, that provide food throughout the winter.
Although nonnative honeysuckle can be an invasive nightmare in our native ecosystems, I grew up with it as part of the Virginia suburban landscape, so I’ve always had a fondness for its aroma in summer. During my years in the Northern Plains and the Pacific Northwest, I pined for that smell. When I became a master naturalist, I spent many hours removing it from sensitive ecosystems in Shenandoah National Park and other places.
However, in learning more about honeysuckle since I moved back to Virginia, I’ve also become aware that its leaves, which stay green in winter, are an important food source for some of our native wildlife, including deer. Now, knowing that robins and other wildlife also rely on the berries makes it increasingly harder to loathe honeysuckle, even the invasive, nonnative species that grows throughout the commonwealth.
Focusing mostly on a single food source this time of year does have its downside. Bacteria and yeast spores feeding on the sugar in fruits, including berries, can cause fermentation, so sometimes the wildlife consuming them, including robins, become intoxicated from eating large amounts. Eating some fruits can even be lethal, according to Learner.org. Fruits from European bush honeysuckles, nightshades, Chinaberries and chokecherries, for example, can produce other kinds of toxins that can paralyze nerve centers and cause vomiting, convulsions and even death in animals.
The American robin’s diet is actually more diverse than most people would think, depending on the season. Along with earthworms, robins eat snails and other invertebrates and even, on occasion, shrews, small snakes and aquatic insects, according to All About Birds. The robin’s taste for fruits is also wide-ranging and, along with honeysuckle berries, includes native hawthorn, juniper and dogwood berries, chokecherries and sumac fruits. According to the website, one study suggested that robins “may try to round out their diet by selectively eating fruits that have bugs in them,” which would add needed protein and fat.
Although the last two winters here in Virginia don’t seem that mild, 2014 was the warmest year on record globally, according to the National Oceanic and Atmospheric Administration’s National Data Climate Center:
“The globally averaged temperature over land and ocean surfaces for 2014 was the highest among all years since record keeping began in 1880. The December combined global land and ocean average surface temperature was also the highest on record.