http://www.nature.com/nsu/031124/031124-3.html
Chicks unite to increase parent-pestering
Coordinated begging extracts more food.
26 November 2003
JOHN WHITFIELD
Children accompanying their parents on Christmas shopping trips: take a
tip from black-headed gull chicks, and team up with your siblings to
increase pester power.
Gull nestlings put aside their differences and coordinate their begging
to extract the maximum amount of regurgitated food from mum and dad,
French researchers have discovered.
It flies in the face of conventional wisdom - children should fight
each other for the biggest share of parental care. "Competition should
increase with the number of chicks, but that's not what we found," says
Nicolas Mathevon of Jean Monnet University in Saint-Etienne.
But offspring are also at odds with their parents, who might want to
hold back their generosity for the benefit of future broods. This is
the first time that a brood has been found to coordinate their efforts
in the struggle for a meal, says Mathevon.
Watching gull nests from a floating platform nearby, Mathevon and
colleague Isabelle Charrier saw begging decrease as the number of
chicks rose from one to three 1.
Chicks in more crowded nests begged less, saving their energy. Begging
became more coordinated and solo begging bouts declined as the nest
filled.
The tactic exploits an adult black-headed gull's habit of ignoring who
the beggar is and simply reacting to the overall amount of begging
coming from the nest, the researchers conclude. Instead of rewarding
loudest chick, the parents regurgitate food onto the ground - at which
point, presumably, the chicks' solidarity breaks down and a
free-for-all ensues.
In other species, such as warblers, the parents dish out food
individually, so each chick must battle its siblings for the maximum
share.
References
Mathevon, N. & Charrier, I. Parent-offspring conflict and
sibling coordination in gulls. Proceedings of the Royal Society B ,
(Suppl.), doi:10.1098/rsbl.2003.0117 (2003).
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