Scientists from the University of Warsaw and Adam Mickiewicz University in Poznań studied the little crack, an extremely secretive bird species living in Poland. It turns out that they can sing in duets, which are among the fastest and most coordinated in the bird world. The results of the study were published in the journal “Proceedings of the Royal Society B: Biological Sciences”.

The research was conducted by Dr Jan Jedlikowski from the UW Faculty of Biology and Ass. Prof. Paweł Ręk from the Faculty of Biology, Adam Mickiewicz University in Poznań.

According to Dr Jedlikowski, the research was complicated because little cracks (Zapornia parva) are very secretive and inhabit bodies of water covered with dense reed beds. Therefore, the fieldwork was conducted in the Masurian Lake District, near the Urwitałt station of the UW Faculty of Biology.

“The birds’ vocalisations and behaviour were recorded using directional microphones, automatic sound recorders, and camera traps. Additionally, the song of a single individual was played from a loudspeaker to some birds, and in response, the greenfinch precisely matched its song tempo to the playback, creating a coordinated duo,” describes Dr Jan Jedlikowski.

A Perfect Duo

In the tropics, the breeding season is significantly longer, allowing partners to remain in stable pairs for most of the year. Passerine birds, which have the ability to learn songs, therefore have time to memorise their partners’ repertoire and the order of syllables, allowing them to increasingly coordinate their voices in a duet. Research conducted by Polish scientists shows that it is possible to perfectly harmonise their voices in a duet without any prior rehearsal. Such duets can also be heard in Poland.

Little cracks can “match” their voices almost immediately after pairing up. They can even do this to a recording played from a loudspeaker. This demonstrates that little cracks are capable of producing coordinated song spontaneously, without the need for prior “practice”. In comparison, in passerine birds, perfecting a duet song typically takes several weeks,” says Dr Jedlikowski.

The research is important for better understanding the vocalisations of non-passerine birds, as it indicates that species lacking complex vocal abilities or the ability to learn songs can produce remarkably coordinated vocal signals.

In the case of the little crack, the duet formed by a male and female is unique, as the partners intertwine their voices with a precision unparalleled even among passerine birds – the intervals between their calls are just 14 milliseconds.

These results suggest that the mechanism enabling the coordination of little cracks’ calls differs significantly from the way passerine birds produce duets. In little cracks, synchronised rhythm and maintaining a constant song tempo likely allow them to predict when their partner will pause, enabling them to perfectly match their vocalisations.

Further research by the scientists will aim to determine which mechanisms actually allow the little crack to precisely coordinate their voices and what information might be encoded in the duets they produce.