Birds learn songs in two forms: innate, the vocalization that is part of the genetic “package” of the species, and learned. That, like in humans, are the vocalizations learned and influenced by the environment. Only three kinds of birds are known to learn vocalizations this way: hummingbirds, parrots, and passerines (also known as songbirds).

For a bird to learn a vocalization it needs to have a tutor. In healthy populations, tutor availability is high, which increases the chance of young birds to incorporate rare syllables/dialects into their vocal repertoire. But what happens when the population is decreasing, and not many tutors are available?

Research conducted on 146 wild male Regent honeyeaters, an endangered passerine species in Australia and published in the Royal Society showed how the decline of the population affects the vocalization quality of the bird. Because there are few adult male honeyeaters remaining in the wild, young birds are not able to find enough tutors to learn their specific vocalizations. Instead, they are incorporating the vocalizations of other species into their own. 

In the future this interspecific vocal learning will create a problem when the birds try to find a mate and reproduce due to the “hybrid vocalizations” not being attractive to the females. To help the species, one of the most important conservation actions is a captive breeding population that aims to boost the population by releasing individuals into the wild. The researchers also evaluated the vocalizations of individuals held in the captive breeding program and found that individuals living in captivity display a shorter and less complex vocalization compared with their wild relatives. These findings may affect the success of the future reintroductions and the fate of the species to avoid extinction.

The results show how the decline of song complexity could reflect the challenges juvenile birds are experiencing in the wild in order to survive. Finally, the research highlights how important it is to consider behavioural aspects in the recovery plan of endangered species.