The kingfisher (Alcedo atthis) has extremely keen eyesight with built-in polarizing filters to eliminate water surface glare. From its perch beside a river it can easily spot a minnow, gudgeon, stickleback or similar small fish as it passes across the stones on the bottom. But when the bird dives into the water, arrowing down with its long, sharp bill, it can no longer see what it is doing and has to rely on memory to catch its prey, which is why it occasionally misses its target and emerges with a pebble in its beak. If it catches a fish it takes it back to its perch, beats it against the branch until it is dead and eats it head first.
