MOBBERS GET MATING RIGHTS
MALE BIRDS ARE MORE LIKELY TO RISK THEIR LIVES WHEN THEY HAVE FEMALES TO IMPRESS.
When crows mob buzzards or songbirds mob owls, they are risking their lives to evict a dangerous predator from their patch. But there may be more to the behaviour than simple defence. According to new research, they might be showing off, too.
“Mobbing is a very risky and energetically demanding behaviour,” says Filipe Cunha of the University of Zurich, who led the work. “Other researchers have suggested that it could be used by males to advertise their qualities to potential mates. But, there was
BBC Wildlife no empirical evidence for it until now.”
The idea goes that a male’s skill and bravery in seeing off predators provides females with clues about their athletic and parental prowess. And it seems that males are only too willing to oblige.
The team studied how males and females of 19 species of Brazilian birds responded to models of predatory owls. Not only were males more likely than females to mob, but they did so more intensely when females of their own species were watching.
“Behaviours can have multiple functions, and some males seem to use it additionally as an opportunity to show off,” Cunha told BBC Wildlife. It might also be a form of group-bonding or be used to teach young birds about which species pose a threat.
It is not yet known if sexual bravado is a factor in mobbing behaviour generally – whether it influences the mobbing of raptors by corvids, for instance. Rather little is known about the biology of the 19 Brazilian species, and it may depend on the mating system of the species involved. In species where females compete over males, for example, are females more likely to take on more of the mobbing duties?
The bottom line, though, is whether potential mates find these displays of derring-do attractive, says Cunha. “Are these brave males chosen by females for mating?”