Wintering robins

Not every bird flies south for the winter

SOUTH NEWFANE — It was a clear, crisp, December day. The mid-afternoon sun gave a warm golden glow to the southern flank of Black Mountain along Rice Farm Road in Dummerston. We were winding down our long day on the Christmas Bird Count. We stopped to do a quick check of the scrubby fields, not expecting to find much. We could not have been more wrong.

In the shrubby berry bushes, we first heard cedar waxwings, then saw them moving rapidly, voraciously feeding on the fruit. Accompanying the thin buzzing of the waxwings was another very familiar sound: the rattling call of robins. We began to count them; after a few minutes we stopped counting and settled for an estimate which was more guesstimate: perhaps 250 robins were working between the woods, shrubs, and fields.

Once robins have completed their breeding season - which may involve raising three broods - they begin to collect in flocks of often hundreds or thousands. As the season progresses, their diet shifts from animal protein during spring and summer (earthworms, grubs, insects and the like) to vegetable matter: principally fruit in the fall and winter.

These large flocks wander, roam, and migrate. My late October trip to Cape May coincided with the passage of robins through southern New Jersey. Huge numbers of robins fell out of the morning sky after their night flight, feeding on juniper, winterberry, bittersweet, sumac, and other berries.

Not coincidentally, the robins' descent into the trees and shrubs was followed by sharp-shinned and Cooper's hawks.

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The American Robin is one of the most widespread, familiar, adaptable, and successful species in North America. Except for southern Florida, extreme southern Texas, and the southern Arizona and California deserts, it breeds throughout the continent, north to the Arctic treeline.

As winter approaches, it abandons its northern range and heads south. Most range maps show it absent from the northern Rockies, northern Great Plains and most of New England in the winter - but not necessarily. I saw many wintering robins when I went to Montreal a few winters ago in pursuit of the Great Gray Owl.

Unfortunately, that wonderful piece of folklore, “Spring is on its way, I just saw the first robin,” just isn't true. We can find robins just about anywhere in the Lower 48 in winter. Although they typically overwinter in large flocks, they can be very nomadic; if their nomadic ways don't intersect with our ways, then we conclude that they're not here; they've gone south.

The robins nesting in our neighborhood have probably gone south, and the hardier birds which breed far to the north have moved down to replace them. But, through all of North America, there's little variation in the American Robin (Turdus migratorius), an indication that breeding populations are constantly being mixed.

Only in “The Sibley Guide to Birds” are regional variations noted, and those variations are minor: Western Robins have limited white tail corners; Atlantic Canada Robins have a blacker nape and upper back.

The species name, migratorius, does suggest that a characteristic of the robin is its migration. It wanders (migrates) all over the place.

The American Robin is a thrush, subfamily Turdinae, genus turdus, and is the only member of its genus any of us is likely to see. Rufous-backed Robin and Clay-colored Robin are accidental at a few places near the southern border, and the Fieldfare from Europe turns up in the East only rarely.

The full and official common name is “American Robin,” but Turdus migratorius is so common that almost everyone knows what you're talking about when you talk about “robins.”

Nevertheless, we should never underestimate grammar's ability to create confusion. When looking for information, I Googled “winter robin” and found many articles referring to, or even titled, “Winter Robin,” with capitals, which reads, and sounds, like the common name of a bird species - and I have occasionally had to explain otherwise.

“Winter robin” refers to an American Robin wintering in a wintery area - one staying the winter, or being seen during the winter. It might better be referred to as a “wintering” robin.

Not all robins abandon our north country for the South; not all robins pass through our north country for more temperate winter climes. Some robins, probably from farther north, stop here, and may even overwinter with us. They are wintering.

Don't be surprised to see robins throughout the winter, as they're warm-blooded, have remarkable insulation from their down feathers, and can maintain body heat through a cold night by shivering. They can survive as long as they can get enough food during the day to replenish their fat stores.

There are factors which will affect whether you see robins during the winter. The greatest correlation is snow cover. Data from the “Great Backyard Bird Count,” done annually in mid-February, indicate that the probability of seeing robins drops dramatically in areas with even just a few centimeters of snow cover.

Unusually low snow cover often results in unusually high numbers of robins, a pattern we've seen over several years of accumulated data. It seems that robins, which are primarily ground feeders, avoid snow-covered areas.

Robins are self-sufficient and quite capable of finding their own food sources. If they appear around backyard feeders, it is because there is some other food source. They do not eat bird seed; their stomach and intestines are not adapted to such food.

Some people have enticed robins to bird feeders by putting out cut fruits (apples, pears, cranberries, blueberries), softened dog food, or a variety of worms. The problem is that most robins have never heard of such a thing as a bird feeder. It just doesn't occur to them to seek human handouts.

It has been suggested that putting out “robin food” during severe weather might be helpful, but it is more likely that the squirrels will find the food before the robins do.

So don't be surprised if you see robins this winter. They're American Robins which are wintering - hence “wintering” robins. Their rattling call can brighten the dreariest of winter days - and should any of those winter days turn pleasant and mild, they are likely to burst into cheerful caroling.

Good birding!

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