Whiffling

Whiffling is a term used in ornithology to describe the behavior whereby a bird rapidly descends with a zig-zagging, side-slipping motion. Sometimes to whiffle, a bird flies briefly with its body turned upside down but with its neck and head twisted 180 degrees around in a normal position. The aerodynamics which usually give a bird lift during flying are thereby inverted and the bird briefly plummets toward the ground before this is quickly reversed and the bird adopts a normal flying orientation.[1][2] This erratic motion resembles a falling leaf, and is used to avoid avian predators or may be used by geese (family Anatidae) to avoid a long, slow descent over an area where wildfowling is practised.[3]

Whiffling is a behaviour some birds perform before landing.

The behavior is seen in several species including lesser yellowlegs (Tringa flavipes), the black-tailed godwit (Limosa limosa), the northern lapwing (Vanellus vanellus), geese (e.g., pink-footed goose (Anser brachyrhynchus)), three species of scoter (Melanitta), and other members of the family Anatidae.[4]