Helen via email asked:
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?
The quick answer is that it might be the case. Most birds donít 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 itís perfectly possible that they do too.