For the Birds Radio Program: Swallows in Winter
In the dead of winter up here in the frozen northland, we can only imagine swallows darting about, daintily catching flying insects. But in some areas of the U.S., swallows are a regular bird in winter, and in the tropics and beyond, swallows are abundant this time of year.
The Tree Swallow is the hardiest member of its family, the only one that normally winters along the South Carolina and California coasts, with some hardy individuals remaining as far north as Long Island. Oddly, the features of this species that make it hardier than its relatives are in its guts. Tree Swallow intestines are longer than those of other swallows and harbor a special bacteria that produces an enzyme that breaks down wax. These two features allow Tree Swallows to digest berries and some other plant material that other swallows can’t. So when temperatures are too low for insects to survive or remain active, Tree Swallows can still get usable calories, giving them the energy to shiver to keep up their body temperature for survival. Under these conditions other swallows would simply starve or freeze to death.
Despite their intestinal fortitude, most Tree Swallows winter in Florida and along the Gulf of Mexico from Mexico to Central America. Recently, some have even been discovered wintering in Venezuela, Guyana, and off Trinidad and Tobago. By February, some are starting their migration north, so when I’ve been to Texas in mid-February, I’ve sometimes seen huge flocks wending their way north. They’ll reach northern Minnesota by late March.
Our lovely Barn Swallow—the one Aristotle referred to when he said that “one swallow does not make a summer” is the most widely distributed swallow in the world, breeding throughout North America, Europe, and Asia, and wintering in Central and South America, the Mediterranean, the Middle East, sub-Saharan Africa, India, Indochina, Malaysia, and Australia. Long ago, Barn Swallows nested primarily in caves, but now they breed almost exclusively on man-made structures, from bridges to eaves. This habit makes this lovely bird with its graceful, long tail one of the more conspicuous and beloved birds. In 1923, William Dawson wrote in The Birds of California:
One hardly knows what quality to admire most in the Barn Swallow. All the dear associations of life at the old farm come thronging up at the sight of him. You think of him somehow as part of the sacred past, yet here he is today as young and as fresh as ever, bubbling over with springtime laughter.
Of course, even if Barn Swallows continue to be abundant almost eighty years later, they aren’t abundant in north country today—not in January. We look forward to seeing our first one of the millennium at the end of April or early May, unless we ourselves get an opportunity to migrate south first. But it’s fun imagining them spending their high-speed days in the tropics, and wondering if they’re any better at understanding Spanish and Portuguese than they are at English.
Our other swallows—the rough-wing, Bank and Cliff Swallow and the Purple Martin, are all flying daintily through the air in Central and South America right now, but days are already slowly growing shorter down there, and they’re starting to think about returning to us. As we look at northern owls and shivering chickadees and a frigid landscape with deepening ice, already the rotation and revolution of the earth are bringing forth the changes necessary to carry our wandering swallows home to us in time to produce a whole new batch for a whole new millennium.