How do elongated wing or tail feathers help some male nightjars during courtship?

In some male nightjars, elongated wing or tail feathers function as specialized signals during courtship displays. These feathers, which are often lost after the breeding season, serve as visual indicators to attract potential mates.1

By developing such elaborate and conspicuous features, males provide a clear signal that can be used by females to assess male quality. Because these displays can be costly to produce or dangerous to bear, they are often considered honest indicators of a male's fitness. These specialized traits are part of a broader suite of courtship behaviors in the order Caprimulgiformes, which also include the flashing of white feather patches that are otherwise concealed when the bird is at rest.21