MOBBERS GET MAT­ING RIGHTS

MALE BIRDS ARE MORE LIKELY TO RISK THEIR LIVES WHEN THEY HAVE FE­MALES TO IM­PRESS.

BBC Wildlife Magazine - - Wild News -

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?”

Mob­bing a preda­tor is risky but could be ben­e­fi­cial in more ways than one, de­pend­ing on who is watch­ing.

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