Speaking of Nature: The tree swallow
Bill Danielson photo
An adult tree swallow can effectively claim a nest box by simply plugging up the entrance with its body.
Bill Danielson photo
A young tree swallow begs for food as one of its parents attempts to land.
One of my favorite things to do on a summer evening is to sit on my deck and soak in the sights and sounds of the evening. There is an open meadow down the hill from my house and it’s bordered on three sides by trees. So, as I gaze down upon this field it is as though I am looking into an amphitheater. The stage is the meadow itself and the set is the backdrop of forest.
My deck is on the east side of my house, which allows me to sit in the shade starting at around 4 p.m. My deck is also raised off the ground, which gives me the feeling of sitting in a private box in the mezzanine of a grand theater. I’ve attended the same show now for years and I never get tired of it. The actors are the same, but the direction is always a little different from one performance to the next; subtle variations in timing and lighting that make every performance unique.
Of the many actors that grace this stage, the ones I have the greatest affinity for are the tree swallows. They are some of the most adorable birds in the world, but what I most enjoy are their splendid aerial skills. Summer evenings just wouldn’t be the same without them and I am so eager to see them every year that I actually keep track of the date of their arrival, which is remarkably consistent from year to year. This year, they arrived on April 4, whereas in 2013, 2012, and 2011 they arrived on April 6, April 6, and April 9 respectively; those subtle variations on direction I mentioned earlier.
First the swallows appear on stage with a flourish. They spend a lot of time wheeling and turning in the open air above my back yard and they take great interest in the nest boxes that I have put out for them. There are always more swallows than there are boxes and that doesn’t include the fact that there are other possible tenants that have their eye on a hot summer rental. House wrens can be feisty competitors for real estate and bluebirds can be fairly pushy, too.
One of the things that varies from one year to the next is the official winner of each of the boxes. If one assumes that the birds are the same individuals, then there might be a little logic this variety. Sort of a, “I didn’t like that box last year, so let’s try a different one dear,” kind of thing. But there is also the clear possibility that the birds are not the same individuals from one year to the next. A particularly aggressive house wren may claim a particular box one year, only to be driven off by an even more aggressive tree swallow the next.
There is one box that is particularly close to my deck and I have enjoyed watching the bickering and fighting that has been going on ever since the birds entered the nesting phase. A pair of tree swallows claimed this box early, but a house wren decided it wanted to put in a bid of its own. I was actually watching the conflict for myself just last week when a wren made a dash for the entrance to the box while the swallows were in the middle of a shift change.
The wren was almost instantly engaged in a fight and the swallows firmly showed the wren the door. I haven’t seen the wren make any further attempt to dislodge the swallows from the box and I have seen a swallow standing guard over the nest every day since. The swallows have clearly won the day and are now incubating eggs.
Even if I hadn’t seen the swallows at the nest box, it would be easy to tell who was in residence by simply opening the box and doing a quick nest inspection. Swallow nests are instantly identifiable by their construction. A foundation of soft grasses will have a cup-shaped depression in the middle of it and that depression will be filled with feathers. What is really surprising about these feathers, however, is the type of feathers they are.
Tree swallows must spend an inordinate amount of time exploring the “local” ponds and rivers in an area because they always manage to find a huge number of duck feathers for their nests. The breast feathers of waterfowl seem to dominate the nest, but the variety of feathers is astounding. I’ve found mallard feathers sitting beside guinea fowl feathers and chicken feathers. But no matter the source, they are always the soft, fluffy, small-shafted breast feathers that are assembled into the most luxuriously soft nest you could ever imagine.
And then there seems to be a signature feather that every swallow nest simply must have. I don’t know how they manage to find them so consistently, but almost every tree swallow nest I have ever found seems to contain the curly tail feather of a male mallard. Other species do this sort of thing, too. For instance, the nests of great-crested flycatchers always seem to contain at least one shed snake skin. It’s some sort of aesthetic compulsion; evidence that style and fashion are not unique to humans.
Once the nest has been finished, the female will lay a clutch of four to five white eggs. Imagine a chicken egg about the size of a peanut that has been removed from its shell and you’ve got the right idea. The female will lay an egg a day until her clutch is complete, then she will incubate the eggs for about two weeks. The male does not share in any of the incubation duty, but he is very important for he is the great defender of the nest. The female, tucked away inside her cavity, would be quite vulnerable without him.
Once the eggs hatch, the swallows enter the next act of their little drama. The male shifts from pure guard duty to provider and he must do a lot of work to catch enough food for his growing chicks. The female must stay with her young while they are very small because they are vulnerable to attacks by wrens and house sparrows, but after a while there is less need for her to be present at all times. This generally coincides with the shrinking of extra space in the box as the chicks grow ever larger.
Eventually, both parents will be in a constant search for food to satiate the huge appetites of the chicks. One year I was able to set up my camera and watch the adults bring one morsel after another to what looked to be a fully-grown chick that plugged up the entrance of the box and greeted its parents with a huge open beak. The chick was fully grown and fully feathered, but it lacked the metallic blue sheen on its feathers and it had the bright red throat with the bright yellow outline that served as a bull’s eye for a parent delivering food.
For now, however, we are still in Act 2 of the season. Fathers will perch proudly by their nests, daring anyone to trespass. Or, they will spend their time diving and swooping in the air above my field, occasionally delivering little treats to their mates. Summer is still not officially here and it will be weeks before we see any hint of baby swallows peering out the portholes of their nest boxes. But, the behavior of their parents will betray their presence long before they actually make an appearance.
All I have to do is watch and wait. Not a bad bit of business at all!
Bill Danielson has worked as a naturalist for 16 years. In that time, he has been a national park ranger, a wildlife biologist and a field researcher. He currently works as a high school chemistry and biology teacher. To contact Bill, or to learn more about his writing, visit www.speakingofnature.com