How do caprimulgiform calls help birds recognize members of their own species?

In the order Caprimulgiformes, vocalizations serve as the primary signals for territorial and mating purposes. While these birds utilize a variety of sounds—including nasal booming, hooting, croaking, and churring—the primary song is the most important mechanism for species recognition.1

Each species possesses a distinct, well-developed vocal pattern, which is often so characteristic that it has led to the onomatopoeic naming of birds such as the whippoorwill and chuck-will’s-widow. Because these songs are unique to each species, they allow individuals to identify members of their own kind effectively. In addition to these vocalizations, some species supplement their communication with mechanical sounds produced during displays, such as wing claps and whirrs.1

Notably, the oilbird is an exception, as it appears to lack a primary song, likely because its gregarious lifestyle makes such a signal superfluous. Instead, it relies on echolocation clicks for navigation in darkness.1