快猫短视频

BARN owls have the politest children. Instead of badgering their parents and
fighting over the next meal, chicks negotiate with each other so the hungriest
can eat first.

Most scientists have assumed that nestlings cry out purely to attract the
attention of their parents. But in many bird species, chicks call all night,
even when the parents aren鈥檛 around. Zoologist Alexandre Roulin wondered whether
these nestlings are actually communicating with each other.

So Roulin, of the University of Bern, Switzerland, and his colleagues chose
two siblings at random from broods of barn owls (Tyto alba) and gave
one of the chicks dead mice to eat during the day. They found that the hungry
nestling cried far more often during the following night than the chick that had
eaten. But once the hungry chick had been fed, its sibling started to beg
more.

In another experiment, he found that the more siblings there were in a nest,
the less the chicks called out. It鈥檚 not what you鈥檇 expect if the chicks were
all trying to shout each other down.

The team think the chicks don鈥檛 beg when they only have a small chance of
getting the food. 鈥淚f one nestling is more hungry than the other, the value of
the food for it is higher,鈥� explains Roulin. 鈥淎 hungry nestling will fight
physically for the prey.鈥�

In this scenario, he says, it鈥檚 not worthwhile for the less hungry nestling
to compete for the food it is unlikely to win. So instead, the chicks monitor
each other鈥檚 hunger levels by the intensity of each other鈥檚 cries. The upshot of
these negotiations is that the less hungry birds back down, electing to save
energy and wait their turn.

Becky Kilner, a zoologist at Cambridge University, says the work is an
interesting new approach. 鈥淣obody has really looked before at the situation of
nestlings communicating in the absence of the parents,鈥� she says. She wonders
whether the chicks of other species behave in the same way.