Animals can tell whether a bird is a friend, a predator (enemy), or a meal (prey) by looking at their silhouette.
A silhouette is the dark shape and outline of a person, object, or animal.
A silhouette can show the size of the bird, the shape of the wings, the shape of the beak, and the shape of the claws.

Starling silhouette

Ibis silhouette

Robin silhouette

Ostrich silhouette

Cormorant silhouette

Hawk silhouette

Bird silhouettes, Source: imgarcade.com
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM