For a long time, we thought baby birds only made noise after hatching. But it turns out that they ‘speak’ while still inside their eggs.
Unhatched chicks make two kinds of noises: peeps and clicks. Peeps are made to communicate with the mother – for example, to let her know how close to hatching the chick is – while clicks are directed at unhatched siblings.
Clicks are technically not ‘calls’ because they are created as a by-product of breathing. Still, these noises act as crucial communication between unhatched chicks, who synchronise their clicks with one another.
The sounds help the chicks to coordinate hatching at roughly the same time. This makes rearing the brood easier for the parents, increasing the chicks’ chances of survival.
But chicks don’t only communicate with one another through clicks. Researchers removed some yellow-legged gull eggs from their nest and played the parents’ alarms, usually made in the presence of predators, to only these eggs.
When put back in the nest, the unhatched chicks ‘vibrated’ their eggs. This passed a message to other eggs in the nest, saying ‘there’s danger outside’. Amazingly, all the chicks – even those who hadn’t heard the parents’ alarms – hatched with behavioural adaptations to a high-predation environment.
