Sky Dancers

A flash of electric blue—over there, no, here, no—it’s over there again! The aerial acrobatics of the barn swallow, swooping inches above fields and water, is spectacular. Its dazzling plumage—blue back, reddish throat, buff breast—and long, forked tail are more readily appreciated when it’s motionless, perched on a branch or wire. That tail, which helps them maneuver, provides an identification mnemonic: the pitchfork is in the barn.

Summer is the season to enjoy these sparrow-sized migrants to the River Towns, when they nest and feed their young during our insect population spike. They’re the world’s most abundant and widely distributed swallow species. Barn swallows in the Western hemisphere live much of the year in Central and South America. As warm weather spreads north, they fly to their breeding range (Mexico and much of North America). Remarkably, individual barn swallows return year after year to the same nest sites. It’s not true that swallows return on the same day each year, but they do typically arrive within a two-week window, usually in mid-April in the River Towns.

Barn swallows are social, forming colonies of around a half-dozen nests. Their nest is a cup of mud reinforced with straw and lined with feathers. It rests on a horizontal support or attaches to a vertical one. Birds may renovate the previous year’s nest, adding a layer of fresh mud. Before extensive human settlement, barn swallows nested in caves, cliff crevices, or bank cavities. They adapted to use barns, stables, and sheds, expanding their range as agriculture spread across the continent.

A nest site must be near mud for construction material. And it must be near flying insects—lots of them. Barn swallows eat virtually nothing else: mostly flies, along with beetles, wasps, moths, and others. Barn swallows on the wing typically chase insects low to the ground, gaping their beak to capture prey. It’s fun to spot a cloud of swallows trailing a plow as it churns up insects. Swallows need wide-open areas where insects proliferate, like fields and waterways. They must fly between their nest and the foraging area, so if there’s a door, it must be open.

Barn swallows are abundant at Tyler State Park in Lower Bucks County, where they nest in boathouses and forage over Neshaminy Creek. At St. Michaels Farm Preserve, in Hopewell Township, swallows use a restored 1840 timber barn, with rafters and open entranceways ideal for nesting, surrounded by fields managed for bird habitat. Limiting insecticides and favoring native plants are the most important ways to support insect-eating birds like the barn swallow.

The nesting season includes two broods that must be hatched, fledged, and fed until they’re independent. By the end of August, barn swallows are heading south.

And just like that, they’re gone! But they will be back. Keep the door open.

Susan Charkes wrote about spring peepers in the Spring issue of River Towns.