Nature Notes: Tree Swallow
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By Ed Robinson
I have often wondered what it’s like to be the second most beautiful creature at a party (admittedly, I am well down the list looking up!). So imagine what a tree swallow feels like with all the fuss about Eastern bluebirds. Yes, bluebirds are just wonderful to look at, with a sunny demeanor to boot. But tree swallows have their own flags to fly, and boy, do they fly! A special thanks to Jeanne Brooks who gave me the prod to prepare this article, since she is a big fan of tree swallows.
In recent decades, the US birding community has worked long and hard to build, install and maintain untold thousands of bluebird nesting boxes, and encouraged forest owners to leave dead snags standing to save potential nesting cavities. The great news is that it has worked, bluebirds have moved into new housing and we all enjoy seeing them in their glory. But another beneficiary has been the diminutive tree swallow, since they need holes the same size as the bluebirds and happily adapted to wooden nesting boxes.
At our old farm in NY, I now have nine pairs of nesting boxes installed around the big field and my cabin. In most years, I host one to two breeding pairs of bluebirds. Almost all the other nesting boxes are taken by tree swallows. That’s just fine with me because I find the tree swallows one of the most entertaining creatures on offer. Not only are they some of the most graceful and dramatic birds on the wing, but their social squabbles are always fun to watch.
When I started installing nesting boxes, I was informed they should be paired, within five to 10 feet of each other. While bluebirds are friendly creatures willing to neighbor with other species, tree swallows will accept a bluebird nest nearby, but not another tree swallow pair. Boy, is that the truth! Every spring I watch tree swallows fluttering, diving, pushing and chirping at each other while they sort out the housing options for the season. It’s not unusual to see a pair of bluebirds sitting nearby waiting for all the dust to settle.
In May this year, I took a long morning break to enjoy a sunny morning on the deck of my cabin. Two pairs of tree swallows were having a real donnybrook over a pair of nesting boxes next to the pond. The debate took more than 30 minutes before one pair of swallows yielded and flew off to the next turf fight. To my delight, the winning pair came to rest on the railing of my deck, and rested in the sun for about 10 minutes. You could almost feel their relief that the big fight was over, their nest site for the year secured.
Over the next few days I watched the pair collecting nesting materials, mostly pieces of grass, weeds, moss and pine needles. I would see a tiny head peak through the opening of the box, and then a swallow would drop to the ground for a mouthful of grass. Rather than simply fly back to the box, the swallow would then make a long, swooping glide around the pond, soaring 50-60 feet in the air. I could see no obvious reason for these long flights other than the sheer joy of flying around like an F18 on a glorious morning. I enjoyed every minute of it!
This swallow averages only five inches long, and weighs under one ounce. The beauty comes from an iridescent blue-green upper body, with white underparts. The beak is tiny, and the tail has a pronounced fork, useful for acrobatic flying. As in most birds, the male is flashier in color than his mate for the year. Outside of the mating season, tree swallows are gregarious and can form flocks that number in the thousands, useful for protection from predators like the raptors.
Tree swallows enjoy open terrain near water or marshes, lakes or meadows. They prefer open spaces, those where plenty of flying insects will be available for food. These little beauties raise heck with flies, mosquitoes, grasshoppers, spiders, beetles and the like, usually grabbing their food on the wing. Later in the season, they also dine of berries of all sorts, especially bayberries, allowing the birds to survive some pretty cold weather, if necessary, thanks to berries that hang on long into winter months.
After breeding, the female sits on her eggs for about two weeks. The nest can contain up to seven eggs, with four to five being more common. Feathers of other birds are used as a soft, warm lining for the nest. The male sticks around to help feed the nestlings, but the female does the brood work in the box. The babies take flight in about three weeks and learn to soar on the light breezes.
The tree swallow migrates long distances each year, from the northern US and Canada to Mexico, the Caribbean and South America. Like hummingbirds, it must take tremendous reserves of energy and constant eating to sustain these small birds on such long flights.
While tree swallow populations were seen to fall by roughly 50 percent after the 1960s, in recent years there is evidence that they may be increasing in numbers while they are also expanding their territory. All of that is fine with me, because I just love these beautiful birds in all their moods, especially on the wing.