The African Fish-eagle (Haliaeetus vocifer) is confined to Africa and seen near most waterways south of the Sahara. It feeds mainly on fish, with each pair defending a relatively small territory. Perched high on a tree, it regularly belts out a gull-like laugh to keep in contact with its mate and to warn off intruding fish-eagles.
This drama is being played regularly for the benefit of tourists. The local guide stuffs a fish with balsa wood to keep it afloat. He then throws the fish into the water and whistles loudly to the eagle. Obviously the bird is used to being fed this way and responds to the call.
All you need do is sit back with your camera ready and shoot your multiple sequential shots as the fish-eagle zooms in.
Once the eagle spots the fish, it lunges from its perch and swoops down low over the water (above left). The sight of this large raptor sailing down with its prominent white head flanked by a pair of huge black wings that span some 2 metres is a stunning sight.
When in flight, the raptor has its feet stretched back and the toed tightly clutched. As it nears the water surface, it lowers its pair of feet and un-clutches all eight toes to reveal the eight long, curved and sharply pointed claws (above right).
Once the prey is targeted, the bird plucks it from the water surface, gripped tightly within the grasp of one set of talons, and flies off (below left).
The takeoff is preceded by the upstroke of its pair of huge wings (above right) before the powerful down stroke that easily gets it airborne again (below left). Subsequent flapping of its powerful wings takes the bird back to its perch or to dry land to enjoy its meal.
During the upstroke, the resulting air pressure forces the primaries feathers to be twisted open, resulting in less resistance to the air. Once the wings are fully raised (above right), the downstroke causes air pressure to push the broader inner vane of the primaries up against the outer vane of the feather over it (below left). This produces an unbroken surface, thus the resulting lift (below right).
All images by Willis.
This post is a cooperative effort between www.naturepixels.org and BESG to bring the study of bird behaviour through photography to a wider audience.