Published: September 27, 2024

Tree swallows can form shapes in the sky as they fly. (Photo: Mark Seth Lender)

Living on Earth's Explorer-in-Residence Mark Seth Lender elaborates on the huge airborne gatherings of tree swallows called "murmurations."

In the acute and focused eyes of hawks and falcons, movement means Fast Food On the Wing. To a point. When there is too much of a good thing (Kid in a Candy Store?) the result is only confusion. No falcon not even a peregrine will dive through the center of a tree swallow murmuration. It is probable that predators fear collision in such a complex environment but the immediate cause is that picking a single target becomes impossible. Tree swallows that become separate from the murmuration are far more at risk and the ones likely to be taken.

From the POV of tree swallows, birds of prey are not the only force of nature that is of concern. We have a lot of weather here in Fall. Storms bottle up migrations. Early morning, just before sunrise, I saw a large number of tree swallows heading the wrong way, towards the Connecticut River not away from it, driven back. Sudden weather turned them around. They were not expecting that to happen or the night before they never would have started out. They needed to be far south of here. Now they will have to do it all again.

Back to Mark Seth Lender Field Notes

Links

Listen to the essay

Mark Seth Lender's website