I normally sit next to Box 2, whose pair of Tree Swallows ignore me. They’ve seen enough of me by now to have classified me as some kind of non-threatening creature, as though I were a woodchuck or a cow. But today I decided I’d sit down the row a bit by Box 3, to see how the resident pair there would react.
As soon as I got there I could see something was wrong. One of the swallows was perching oddly on the crossbar, as though one of its legs or feet was injured. The slightly brighter, crisper iridescent blue of this bird’s head and back signalled to me that it was a male.
Since I check boxes every day, and pairs seldom fly until I’m quite close, I really believe I’d have noticed an injured swallow here before. I’m pretty sure this injury, whatever it is, is recent, perhaps very recent.
There is always the risk of injury when Tree Swallows fight over nest sites. Their bills, though small, are sharp. But bills generally inflict injury on the opponent’s head, back or breast. Another possibility is the bird was injured hitting an object as it fell to the ground as it battled with another swallow with legs locked together. The field is studded with stiff broken dead stalks of last year’s vegetation, that could do some damage if hit from above.
I’ll never know for sure what happened, but this swallow is now at a big disadvantage. In addition to dealing with pain, it may now be more vulnerable to avian predators, which are quick to notice and single out injured prey. If it lives and the injury doesn’t heal properly this swallow may have difficulty caring for its feathers and ridding them of parasites. It may have permanent trouble perching on thin vegetation while resting or roosting. It may not be able to copulate, which involves landing on a female’s back and balancing there while making cloacal contact. It may not be able to maneuver through the entrance hole of a nest box, which means it will not be able to feed its young when they are too small to come up to the entrance.
However, perhaps the most immediate issue for this male will be holding on to its nest box, for it will certainly have lost some of its defensive ability, and there are other males floating at the grid who will put him to the test.