Many birds are well aware of alarms from other species and respond to them when danger approaches. However, a new study found that nuthatches living in North America, while recognizing the alarm signal of local titmouse, do not take action directly until they hear the alarm signal of another nuthatch.
Both species of birds that have become the object of research are the black-capped tit (Poecile atricapillus) from the titmouse family and the Canadian nuthatch (Sitta canadensis) - widespread in North America. Like Russian nuthatches and tits, in winter they often form joint flocks and wander in search of food.
The black-capped gadget has a rich vocabulary of vocalizations, including a loud alarm, the sound of which is usually rendered as "Chikadi!" From this sound the bird got its everyday English name (black-capped chickadee). The Canadian nuthatches have their own alarm signal, having heard which, they usually unite and jointly attack the bird of prey approaching them.
Bird watchers Nora V. Carlson of the Max Planck Society of Ornithology Institute, Erick Greene of the University of Montana, and Christopher N. Templeton of the University of the Pacific found that the alarms of Canadian nuthatches differ depending on which whether they noticed the predator themselves or did they hear the alarm signal of the black-headed tit. Researchers have observed the reactions of birds when approaching passerine owls or the Virginia eagle owl, their common enemies.
When a nuthatch sees an approaching owl, it emits an alarm signal characteristic of nuthatches and takes off to attack the predator together with other nuthatches. If a nuthatch heard the signal "Chikadi!", But did not see the danger himself, it starts to emit an alarm signal that sounds a little differently, and does not take any other action until it hears a confirmation signal from another nuthatch.
Scientists believe that, reacting to every signal from the chicks, nuthatches in the event of a false alarm will waste too much energy, but completely ignoring these signals would be dangerous. Therefore, nuthatches, in the words of the authors of the study, "carefully retweet" the signal of the tits. Eric Green explains that these nuthatches are reporting: "We are on high alert, as we learned from the tits that something is happening, but we have not verified this information."
The research is published in the journal Nature Communications.