600mm on a tripod and about 150 hours of shooting a pair of kingfishers. After a while you start to notice their patterns and habits so it's possible to predict (to a degree) what they are going to do.

This image is one of a sequence of 6 frames of the bird going into a hover just before landing on a favorite perch. The hover wasn't expected but I already had the bird in the frame so I just hit the shutter and prayed lol