Scientists have found that black grackles listening to an audio message yellow drevesnitsa about the approach of the breeding of the parasite and can distinguish them from signals of other dangers. The closer grackles settle for drevesnitsa, the stronger they respond to the voice of the past — it helps them better to protect their nests. Article published in the journal Biology Communications.
Many animals pass each other information, for example, a danger signal, with the help of sounds. Such messages can be overheard and to use other types. This is especially common in birds, they use various voice signals for communication. Different sounds used to transmit different messages — a warning to predators and other dangers, marking his territory, finding a partner, call. Birds that eavesdrop on the signals of other species are also able to distinguish specific sounds and respond accordingly.
Messages about the danger help to protect the nest from predators and nest parasites — birds that put their eggs to strangers. Alert birds that timely notice parasites drove them from the nest and transmit a corresponding signal of danger to their relatives. It can be assumed that those species who do not have their own warning systems, eavesdrop on the messages of others. This is already observed in two species of reed warblers, the nests of which parasitizes the same species of cuckoo. However, these birds transmit a General signal of danger specific set of sounds for messages about the female parasite they have.
Yellow the new world warblers (Setophaga petechia) — the only known birds that have special signal of nesting parasites. In their nests throw their eggs borogravia cow grackles, or volovya birds (Molothrus ater), and at their approach of the leopard make a short sound, in response to which the females fly to their nests and sit on them, physically protecting the clutch from danger. Such a signal the birds used only for messages about parasites, mainly in the period of incubation.