Most Summers, we’ll get several pairs of Barn Swallows nesting in the garage. They’ll raise young in the Spring, and then perhaps try for a second clutch later in the Summer. There are usually a couple of weeks in the Summer when there are fledgling Barn Swallows hopping around the garage, getting into trouble.
It is a vastly entertaining time of year.
Back in August of 2012, a pair of Barn Swallows decided to build their mud nest under the eves of our house, on one of the beams of our roof. Given how late in the Summer it was, I’m guessing it was the Swallows’ second clutch.
What was interesting about this was the Swallows’ choice of nesting location. There were already a couple of Bald-faced Hornet (Dolichovespula maculata) nests under the eves of our house. They were very near the Swallow nest.
One Hornet nest was small, perhaps the size of a baseball, and (as I recall), empty. This one was two or three feet from the Swallow nest.
The other Hornet nest was larger, perhaps 8 inches in diameter. This larger nest was just on the other side of the roof beam from the Swallow nest.
This Hornet nest was growing quickly, and had Bald-faced Hornets coming and going regularly. It had grown large enough that the Hornets were becoming aggressive.
I wasn’t sure what would happen between the Hornets and the Barn Swallows. I assumed that the Hornets would drive the Barn Swallows away. If they didn’t, then I assumed that the Hornets would kill and eat any Barn Swallow hatchlings.
Neither of those things happened. Instead, the Barn-Swallows destroyed the Bald-faced Hornet nest. They’d fly up against the Hornet nest, making physical contact with their bodies and wings. I couldn’t tell for sure if they were scratching or pecking at the nest, but the paper envelope of the larger Hornet nest disintegrated over the course of a few days.
I didn’t see the Swallows catching the Hornets, either, but the Hornets disappeared after the Swallows tore open the Hornet nest’s exterior paper envelope.
Did the Barn Swallows kill the Hornets, or did the Hornets leave after their nest was opened up? I don’t know for sure. I know that the Hornets were actively flying, and upset, when the Swallows were dismantling the Hornet nest.
It’s interesting. In the garage we’ll often have Paper Wasp (Polistes sp.) nests relatively near the Swallow nests. Paper Wasps are usually much less aggressive than Hornets.I’ve never seen the Swallows interfering with the Paper Wasp nests…maybe they do, and I’ve just not noticed it?
Or maybe the Swallows treat Paper Wasps and Bald-faced Hornets differently?
