Date: May 10, 2018
Source: University of Exeter
Jackdaws recognise each other's
voices and respond in greater numbers to warnings from familiar birds than
strangers, new research shows.
The birds produce a harsh "scolding
call" when they spot a predator, calling fellow jackdaws to mob the
intruder and drive it away.
University of Exeter researchers
have discovered that each bird has a unique call, and the size of the mob
depends on which bird calls the warning.
The scientists played recordings
of individual calls and found that the largest mobs assembled when birds heard
the cry of a member of their own colony.
"Joining a mobbing event can
be dangerous, as it involves approaching a predator, so it makes sense for individuals
to be selective in whom they join. Our results show that jackdaws use the
ability to discriminate between each other's voices when deciding whether to
join in potentially risky collective activities," said Dr Alex Thornton,
of the Centre for Ecology and Conservation on the University of Exeter's Penryn
Campus in Cornwall.
"We also found a positive
feedback loop -- if birds joining a mob made alarm calls of their own, this in
turn caused more birds to join in, magnifying the size of the mob."
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