Science Questions

While watching swallows in flight last summer, it appeared that they were rotating in the air around a full 360 degrees, wing over wing. Is this an optical illusion or can they really do it? Helen via email

The quick answer is that it might be the case. Most birds don’t do that because they actually keep their head horizontal in flight, so if you turn 360 degrees you end up turning your head around. The only bird I know that definitely does it is the raven, but swallows are very manoeuvrable so I guess it’s perfectly possible that they do too.

March 2007