Barn and Tree Swallows
Gliding, diving, graceful birds
Acrobats in flight.
On a boring day in May, June, or July you can always sit on the porch with a cool drink and watch the swallows. This year the Tree Swallows won the annual competition for the birdhouse down by the creek, the one with the water view, and the Bluebirds were again relegated to the other two houses along the driveway. I don’t pick favorites as both have great appeal. The birdhouse by the water does have some issues as the smart Fish Crows from the neighbor’s trees are always poking their large bills through the hole, trying to snag a hatchling for lunch. The parents do a brave job driving off the much larger crows, but I fear they are not always successful. That doesn’t seem to stop the swallows from coming back here year after year.
The entertainment is their airshow. Swooping, sharp corners, straight up, diving low over the grass and river, catching insects, eating and drinking, even in flight. In my book only the terns can rival the swallows in aerial acrobatics. The Tree Swallows arrive first in the spring to stake out a nesting cavity, and stay later in the fall since they are the only swallow that can also feed on berries when the bugs are no longer plentiful. The later arriving Barn Swallows almost exclusively build their mud nests on man-made structures–in my yard that’s the underside of the boat dock.
The “Barnies” are the only North American swallow that has that deeply forked swallow tail. It, plus the chestnut colored throat make the ID easy. The Tree Swallows are striking birds with pure white below and metallic blue or green above, depending on the light. These are the most common swallows in the East, but keep an eye out for the Bank S. with its dark chest band, the less sociable and more bland Northern Rough-winged S., and an occasional Cliff S. with its buff rump and forehead.
Then one evening in late July you notice they’re gone. No fanfare or goodbyes, just gone, show’s over. The birdhouse and dock are vacated. And why did they leave so early? There are still plenty of bugs, warm weather and sunshine, and maybe even enough time to raise another brood. But I’ve learned that they are not gone. The swallows haven’t really left for the season yet, but have changed their venue. Just travel a few miles east to the inland fields with power lines or the vast tidal marshes along Delaware Bay and you’ll find them again. You’ll see flocks, sometimes huge mixed flocks of swallows, no longer interested in breeding but now more intent upon consuming large volumes of insects and storing up energy for the coming fall.
The fall migration is a much bigger deal than its spring counterpart. A successful breeding season will swell the flock many times over the number of birds that arrived the previous spring. But there’s danger ahead. Its been reported that the mortality rate for songbirds during the fall migration and at the wintering sites may be as high as 85% due to disease, predators, accidents, weather, etc.
Flocking prior to and during fall migration, and continuing all winter, may in part be a safety mechanism to confuse predators with visual overload. As opposed to most songbirds the swallows migrate in these large flocks during daylight, perhaps relying on visual clues for guidance. This also allows them to feed on the fly. The Tree Swallows will actually undergo a gradual molt during the trip to South Florida, the Gulf coast, Cuba, or Mexico, whereas the “Barnies” wait to molt until they have arrived at the wintering grounds in South America.
So the swallow’s sojourn in their summer breeding grounds appears to be a two part affair. First mate, nest, and raise the young. But when that’s accomplished congregate in great numbers, fellowship, teach the juveniles advanced flying skills, and build up fat reserves for migration. And when the mysterious word is spoken, whether it’s hormonal, sunlight, or temperature, be ready to head south en masse. Their return in the spring will not be in massive flocks but rather in smaller groups of survivors, coming north to start the cycle all over again.