(ORDO NEWS) — Various species of songbirds often form groups and attack predators to scare them away. However, as it turned out, they do this only under certain conditions.
The results of the study showed that birds determine when the danger of a predator attack is greatest, and their number is sufficient to reduce individual risk.
Flight is not the only way that small songbirds are able to escape from predators.
Many such species may congregate and circle aggressively around a potentially dangerous animal, making loud noises. This behavior is called mobbing, and it can be dangerous for both predators and prey groups.
Scientists from the University of Oregon (USA) have shown that songbirds can determine when the risk of attack from a predator is highest, and increase the frequency of mobbing.
It depends on the season and region. And when the risk is minimal, they prefer to avoid or ignore the predator.
The authors of the work studied gnome pygmy owls ( Glaucidium gnoma ) in Western Oregon.
They are small diurnal predators found in western North America. As a rule, they attack small mammals and birds, setting up an ambush from a hidden place.
Mobbing is an energy-demanding behavior, so it is less common in winter when food is scarce.
At the same time, the proportion of birds in relation to mammals in the diet of the northern pygmy owl almost doubles from spring to summer.
In summer, birds become the main food of owls, and just at this time their chicks fledge.
The scientists played recordings of the owl’s call at various songbird nesting sites to provoke mobbing. Overall, it was observed in 8.1% of trials.
At the same time, the peak of mobbing (23%) occurred at the end of summer and autumn. The likelihood of this behavior decreased with altitude, which correlates with fewer owls at higher altitudes.
Tits, red-throated nuthatches, Pacific wrens and gray juncos most often switched to attacking behavior.
Larger species, such as thrushes and jays, which are rarely preyed on by owls, were rarely present in the attack crowd, although they attacked larger owls.
Also, the likelihood of mobbing increased as the number of birds increased.
That is, birds gather in a crowd only if the threat is real, but at the same time they also evaluate the number of relatives ready to join in order to reduce the risk to themselves.
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