Do vocal mimics learn their mimetic songs from heterospecifics or conspecifics?

What is it about?

For thousands of years humans have been intrigued by bird species that produce the sounds of other species. The list of vocal mimics is long and includes superb lyrebirds, European starlings, Chinese blackbirds, and northern mockingbirds. Over 100 years ago scientists began to entertain the possibility that some mimicking species might learn at least some of their mimetic sounds not by copying the original model species (which we term ‘primary mimicry’), but by copying individuals of their own species (‘secondary mimicry’). Distinguishing between primary and secondary mimicry is important if we want to understand how vocal mimics interact with their environment, how their songs evolve over time, and how their brains work. The best method to detect primary versus secondary mimicry would be to observe a young bird as it hears and then matches the songs of their own and other species. Song matching like this occurs frequently in adult mockingbirds, but it is almost never observed in the wild for younger mockingbirds. We therefore propose four strategies for how researchers can identify secondary mimicry by measuring the songs of adults in both the mimicking and model species. We then use each of these strategies to detect likely instances of secondary mimicry among the songs of adult northern mockingbirds. The existence and extent of secondary mimicry in mockingbirds and other vocal mimics still needs more exploration.

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