Twenty bird species understand each other's anti-cuckoo calls
Researchers have discovered that 20 different bird species can recognize and respond to each other's warning calls against cuckoos, a common brood parasite. This finding highlights a rare level of cross-species communication in the animal kingdom. The study, based on observations in Japan, was published on September 25, 2024.
In a groundbreaking study, scientists observed birds in the forests of Karasuyama, Japan, revealing that 20 species share an understanding of alarm calls designed to deter common cuckoos (Cuculus canorus). Cuckoos are notorious brood parasites that lay their eggs in the nests of other birds, tricking hosts into raising their young. The research, led by William Hoppitt at the University of Cambridge and colleagues from institutions including the University of Zurich and Tohoku University, was published in Proceedings of the Royal Society B on September 25, 2024.
The team focused on how birds mob and harass cuckoos upon detecting them. They recorded anti-cuckoo calls from species like the Japanese bush warbler and Eurasian tree sparrow, then played these back to see if other birds reacted. Remarkably, birds from 20 species, including great tits and varied tits, responded aggressively to calls from other species, flying toward speakers and attempting to attack the perceived threat. This behavior occurred even when the calls came from non-social or distantly related birds.
"This is the first evidence that different species can understand each other's alarm calls for a specific threat," said lead author Jolyon Troscianko from the University of Cambridge. The calls, which sound like a sharp 'chink-chink,' are acoustically similar across species, possibly evolving convergently due to the shared danger of cuckoos. In contrast, general predator alarms, like those for cats or snakes, did not elicit the same cross-species response, indicating the specificity to cuckoos.
The study involved over 200 playback experiments conducted between 2018 and 2023. Researchers noted that in areas with high cuckoo presence, such interspecies communication could enhance survival by amplifying warnings. However, the exact mechanism—whether innate or learned—remains unclear. This discovery underscores the complexity of animal social networks and could inform conservation efforts for birds facing habitat loss and invasive threats.
While the findings are limited to this Japanese woodland ecosystem, they suggest broader implications for how animals cooperate against common foes. Future research may explore similar dynamics in other regions or with different parasites.