Smaller bird species will sometimes dive-bomb much larger predators to keep them at bay.
But researchers have found that this behavior not only protects the smaller birds – it also lets males show off to impress the ladies.
This ‘mobbing’ behavior can allow females to assess a males quality, providing clues as to how well he’ll be able to defend a nest or forage.
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The study, which was conducted on a ranch in the Minas Gerais State of south-eastern Brazil, looked at the mobbing behavior of birds where potential prey approach and harass potential predators such as owls.
Mobbing behavior in birds includes calls, aerial swoops and even physical attacks.
For a while researchers thought these behaviors were mainly used as protection against predators – as most predators move away when they’re mobbed.
But mobbing potential predators gives an added bonus to male birds who are able to advertise who has the best physical qualities to impress potential mating partners.
The researchers decided to investigate this further by designing an experiment where model replicas of two owl species were presented to a bird community in south-eastern Brazil.
One model was of a pygmy owl that regularly eats birds, and the other was of a less threatening burrowing owl.
The researchers then measured the size of the mob that assembled, how intensely each individual bird participated in the mock attacks, and if things changed when females of the same species were present.
During these tests, 79 different bird species mobbed the model owls – but data from only 19 sexually dimorphic species were included in the anaylsis of the study.
Sexual dimorphism is when males and females of a species look different and are easily distinguishable, which is why they were chosen to be analyzed in the study.
The researchers found that mobbing was more intense when when the less-threatening burrowing model owl was put out.
This reflects other findings showing that birds know there is a higher or lower risk in harassing certain predators.
Most of the mobs were made up of males, and the numbers in a mob didn’t have an influence on how intensely each male participated in the mobbing.
However, males in all 19 species analyzed were more likely to participate more intensely in mobbing when greater numbers of females from their species were around to see.
‘Females may use these mobbing events to assess a male’s quality, for example their motor skills which allow them to escape from an attacking predator,’ said Dr Filipe Cunha, a researcher at the University of Zurich in Switzerland and the Federal University of Ouro Preto in Brazil and the lead author of the study.
‘This characteristic may provide clues about how well a male will be able to defend a nest or to forage,’ he said.
Dr Cunha said that the recent studies have also shown that mobbing has other important social impacts, such as teaching young birds to distinguish enemies from friends.
The researchers said that the findings help to better understand the evolution of anti-predatory behavior.
Video: Crows Mobbing a Bald Eagle
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Source: dailymail.co.uk
