Sometimes reader mail serves as my calendar. For example, it must be mid winter because I'm getting letters and e-mails about flocks of robins. Does the appearance of winter robins mean spring will arrive early, or are these birds just disoriented? That's the gist of most of the queries. Here's what happening.
Unlike warblers, swallows, and other song birds that migrate to avoid severe northern winters, robins are hardy and flexible. The extent of their annual migration is influenced by several factors, so seeing robins in winter isn't unusual. But even in years when robins escape detection, some while away the colder months in the deep woods where few of us venture regularly. Talk to anyone who hikes the winter woods, however, and you'll hear tales of flocks of robins every year.
Several winters ago robins were particularly common in the northern United States. According to Project FeederWatch results from Cornell University's Laboratory of Ornithology, a woman from Miles City, Montana reported, "In January, my whole town was full of flocks of robins. ... I've never seen so many or seen them stay so long."
Sight to behold
Large winter flocks of robins are typical in the southeastern and Gulf coast states, though serious birders can usually come up with a few winter robins just about anywhere. Nonetheless, large flocks of winter robins are always a sight to behold.
Winter robin abundance is most influenced by two factors: snow cover and food availability. In comparing robin abundance to snow cover, the Lab of Ornithology reports that areas with less than five inches of snow cover typically have lots of robins, while areas with more than five inches of snow cover have fewer robins. Heavier snow cover means colder temperatures and food that's more difficult to find, so robins move south to more favorable conditions.
Furthermore, if food is abundant, robins can thrive in surprisingly cold temperatures if coupled with minimal snowfall. Fruit-bearing trees and shrubs such as cherries and grapes sustain robins during the winter months. Being dietary opportunists, robins remain where food is abundant until supplies are exhausted. Then they move on.
One reason robins may linger farther north, especially during mild winters, is the popularity of ornamental fruit trees in urban and suburban areas. We may plant hawthorns, crab apples, and mountain ashes for their visual appeal, but robins value their fruits. Our horticultural habits have helped create a winter oasis for robins.
Less distance to travel
Another advantage to less frequent and shorter migrations is that robins have that much less distance to travel again in the spring. Thus they can return to their breeding territories earlier and in better condition.
Though people may see flocks of scores or even hundreds of robins during the day while they forage on fruits and berries, the largest and most impressive groups assemble just before dusk. Thousands, and sometimes tens of thousands, of robins roost in conifers or other dense cover. They may be joined by cowbirds, grackles and starlings, also numbering in the thousands. Such a sight is impressive, unless you happen to park your car under the roost tree.
At dawn, these large roosting flocks break up into many smaller feeding flocks that might travel as far as ten to 20 miles to a food source. At day's end, they return to the roost for a good night's sleep.
Readers also often ask if robins can be attracted to feeders. They can, but not with seeds. Try offering raisins, grapes, or craisins. Or, thinking more long term, plant a few fruit-bearing trees and shrubs around the house. Robins also love live food. I've watched hungry robins leave feeders gripping more than a dozen mealworms in their bill.
The appearance of robins is as unreliable a sign of spring as the ground hog and its shadow. More often than not, robins are year-round residents. If you choose to measure the seasons by the occurrence of migratory birds, let hummingbirds and orioles be your harbingers of spring.