Swallows are one of our most familiar and usually welcome summer migrants, heralding summer with all the typically warm and dry weather that goes with it. As a summer migrant, they have some very interesting aspects to their ecology, not least that adult birds will return to the same nest year after year, despite flying to the other side of the world and back each winter.
One really interesting aspect of their behaviour is that Swallows are very aggressive and regularly “mob” potential predators such as cats or, in the photo here, Sparrowhawks. This behaviour is designed to let the potential predator know that the Swallow knows they are there, and so cannot sneak up on them.
Many predators are “ambush predators”, where they in-effect sneak up on their prey. Sparrowhawks do this by flying fast through cover to surprise and flush birds that may be hiding in the cover. The results are that Swallows can look as though they are chasing the bird of prey. This aspect of the Swallows’ behaviour is also very helpful to ecologists surveying birds. Birds of prey are typically scarce in the wider countryside and can be difficult to spot. However, the noise of a flock of chattering Swallows chasing a Sparrowhawk can often draw our attention to them as well so that we can record them.
Of course, in the photo here, taken by one of the INIS Ecology Team, the Swallow probably doesn’t have too much to worry about as the Sparrowhawk already appears to have its hands (or talons) full with another bird which it is presumably taking back to its nest to feed its chicks!