The cuckoo has fascinated observers and researchers of nature for centuries. Its characteristic call is one of the most recognizable sounds of spring. But do all cuckoos, or even all members of the best known species Cuculus canorus, sound the same? Research just published by Polish researchers in the journal "Animal Behaviour" shows that this is not necessarily the case.

'Our research concerned information known from earlier reports that some cuckoos produce sounds with a changed structure, e.g. 'cu-cu-coo' instead of the classic 'cu-coo'. Such vocal aberrations may result from various factors, including genetic mutations, developmental disorders or environmental impact, including radioactive contamination', says Professor Piotr Tryjanowski from the Poznań University of Life Sciences, the first author of the published work.

Its co-author, Professor Tomasz Osiejuk from the Department of Behavioural Ecology at Adam Mickiewicz University, a bioacoustics expert, emphasizes that in the case cuckoos, birds that have a genetically determined song, mutations in the voice structure 'are probably long-term, and their evolutionary consequences are difficult to predict'.

Researchers have long wondered to what extent the changed voice interfere with birds' effective communication. Attempts to explain it have most often been anecdotal, note the authors of the paper point out in a press release sent to PAP - Science in Poland. In the case of the cuckoo, the researchers decided to conduct manipulative field experiments, which unequivocally showed that cuckoos responded primarily to the classic call 'cuckoo', and paid less attention to the aberrant versions. This may mean that males with impaired song are at a disadvantage when competing for females and territory. Interestingly, birds potentially threatened by cuckoo parasitism respond to both song variants, although their reaction to 'cu-cu-coo' is also much weaker.

Another co-author, Professor Łukasz Jankowiak from the University of Szczecin, points out that such vocal anomalies may have evolutionary significance. If aberrations are hereditary and lead to reduced reproductive efficiency, natural selection should eliminate them. On the other hand, if altered vocalizations can help cuckoos avoid confrontations or reduce the risk of mobbing by hosts, they may become established in the population.

Does environmental pollution affect bird communication? It is worth taking a look at research conducted in areas contaminated with radiation, such as Chernobyl, where changes in the songs of many species of birds, including cuckoos, were recorded, we read in the press release. Previous research by Professor Piotr Tryjanowski and colleagues suggests that the number of syllables in cuckoo songs may correlate with the level of radioactive contamination. It is therefore possible that mutations resulting from radiation affect the development of brain structures responsible for sound production.

Can such work have potential for application? 'Potentially yes', Tryjanowski says. 'The discovery of the impact of voice mutations in birds may have practical applications. Firstly, changes in voice may be a biomarker of environmental pollution - analysis of sounds may allow to assess the impact of toxic factors on living organisms. Secondly, the study of compensatory mechanisms in animal communication may expand our knowledge of the plasticity of biological systems'.

'The world of bird sounds is not only beauty and harmony, but also a complex network of biological interactions. Understanding how mutations affect communication can provide key information about the functioning of ecosystems', Professor Piotr Tryjanowski concludes.

'Will we be able to +eavesdrop+ on the condition of the environment based on bird calls in the future? There are many indications that we will', the authors of the published paper confirm.

PAP - Science in Poland

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