What is a distinctive behavior of the American Kestrel often observed in the field?

The distinctive behavior of the American Kestrel that is often observed in the field is tail pumping. This behavior typically involves the bird rapidly moving its tail up and down, which can be seen when it is perched or flying. Tail pumping serves a variety of functions, such as signaling to other kestrels or expressing excitement, and it can also be seen during hunting flights, helping the kestrel maintain balance and maneuverability while searching for prey. This behavior is particularly characteristic of the American Kestrel and can be a key identifier for birdwatchers and ornithologists in the field.

The other behaviors listed are not unique to the American Kestrel. While wing flapping is common among many bird species during flight, ground scratching is associated with birds like quails looking for food, and stationary hovering is a technique seen in larger raptors like hawks and kestrels but not specifically distinctive to the American Kestrel compared to its tail pumping behavior.