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What information is coded in bird alarm calls—a new study from Korea

Source: phys.org

Have you seen small birds nervously jumping up and down the branches and calling at a cat in a park? For a long time, scientists have been interested in what type of information about predators is coded in alarm calls; is it predator’s species identity? Or their size? Or how dangerous it is? A recent study published in Ethology provides new discoveries in this field.

The study carried out by researchers of the Laboratory of Behavioural Ecology and Evolution at the Seoul National University (SNU, Korea) and the Laboratory of Integrative Animal Ecology at DGIST (Korea) with a collaboration of the Museum and Institute of Zoology, Polish Academy of Sciences, has focused on the oriental tit (Parus minor). Oriental tits breed in tree cavities or nest boxes. Therefore, they are protected from predators that cannot squeeze into the nest. However, some predators like snakes can do that. It has already been known that oriental tits give a special alarm call that sounds like rattling when a snake approaches their nest. When nestlings in the nest hear this call, they jump out of the nest. This call is different from a call to a bird predator, like crows, magpies or jays, that cannot enter the nest and tries to capture young birds outside of their nests. MORE

Header image: (A) – A snake (the steppe rat snake, Elaphe dione) found inside of a nest box on top of the nest of the Oriental tit after it ate the nestlings that were in the nest; (B) – a model of a snake on top of a nest box was moved in a naturalistic manner using fishing line from a distance in order to trigger alarm calls in the birds. These tests lasted just a few minutes, they did not cause any harm to the birds, and the recordings of bird responses showed that alarm calls to snakes have special acoustic properties different from calls to chipmunks, who also can enter the nest boxes and eat broods. This suggests that the calls do not carry information about predator’s ability to enter the nest cavity. Credit: Jungmoon Ha, Keesan Lee, Eunjeong Yang, Woojoo Kim, Hokyung Song, Injae Hwang, Larisa LeeCruz, Sangim Lee, Piotr Jablonski.