The birds living in Poland are vocal masters. They have an extremely interesting ability.

An inconspicuous species of bird living in Poland – the little green fowl – can form some of the fastest and best-coordinated duets in the bird world, without any prior attempts at a partner, research by Polish biologists has shown.

The study results were published in the prestigious journal "Proceedings of the Royal Society B: Biological Sciences." As explained by the authors , Dr. Jan Jedlikowski from the Faculty of Biology, University of Warsaw, and Dr. hab. Paweł Ręk from the Faculty of Biology, Adam Mickiewicz University in Poznań , duet singing is not uncommon in the bird world. However, duets are particularly popular among passerines inhabiting the tropical zone. In Europe and other temperate regions, such complex vocal displays are rare.

"In the tropics, the bird breeding season is much longer, allowing partners to remain in stable pairs for most of the year. Passerine birds, which have the ability to learn to sing, therefore have time to memorize their partner's repertoire and the order of syllables, which allows them to better match their voices in a duet," Dr. Jedlikowski explained to PAP.

However, research by Polish scientists shows that it is possible to perfectly harmonize the voices in a duet without any prior rehearsal. Such duets can also be heard in Poland.

The species that produces this unusual song is the little green fowl (Zapornia parva), a rather secretive bird that inhabits wetlands. Dr. Jedlikowski and Dr. Hab. Ręk studied the mechanism and function of this species' song. They found that little green fowls can sing duets with extraordinary precision. In passerines, the intervals between partners' calls typically range from 50 to 500 milliseconds.

A bird of the species Zielonka/photo: Wikipedia, public domain

Meanwhile, in the case of the little crake, these intervals are just 14 milliseconds. Moreover, the birds' song rate reaches up to 30 notes per second. Biologists have determined that this is one of the fastest and most synchronized duets in the animal kingdom.

In their opinion, what is even more surprising is that the Greens do not need to know each other beforehand to "sing together".

- They can perfectly synchronize with a complete stranger almost immediately after meeting - noted Dr. Jedlikowski.

This is achieved by adjusting the rhythm and tempo of their vocalizations. The consistent rhythm and tempo of the song allow the birds to anticipate when their partner will pause and to perfectly match it. Thus, synchronizing the rhythm at the beginning and then maintaining a constant tempo of the song allows the birds to create such a precise duet.

- It's a bit like two drummers who, while beating a fast rhythm, don't hear every single beat, but they keep the tempo and are therefore perfectly in tune - explained the biologist.

In the case of passerine birds, Dr. Jedlikowski noted, their more irregular singing causes individuals to match their voices "note by note," so that the intervals between subsequent calls are much longer than those of the little crake.

The researchers also observed that producing a duet at such a rapid rate of song is only possible when the birds are close to each other. Therefore, they suspect that the information encoded in the duet may relate to the distance between the partners. However, this is just one hypothesis, which the researchers plan to test in future studies.