From an egg to another, birds' chicks seem to communicate with each other, even before hatch, through "vibration", a previously unknown method.
In a study published Monday in the Nature Ecology & Evolution journal, Spanish researchers found during experiments involving unhatched Mediterranean gull chicks that eggs receive warning sounds usually emitted by adult gulls to warn their peers from threats.
Commenting on the findings, experts said "it is an amazing study" that will drastically change the current view about bird chicks. Chicks were long seen as isolated and silent creatures; however, the study showed that they are active and very aware of what happens in their environment, the German news agency reported.
Before the study, it was known that before hatching, the birds' embryos recognize some external stimuli, such as calls, and make their own calls in order to coordinate their hatching time.
But this study, conducted by researchers Jose Noguera and Alberto Vidalo of the University of Vigo, Spain, suggests that experts did not give the birds' prenatal communication the required attention.
The researchers studied a squadron of Mediterranean gulls on the island of Sálvora, off the coast of Galicia, south-west of Santiago de Compostela, in Spain. They found that adult seagulls use warning sounds when seeing intruders such as pheasants, and stand still.
In this study, the researchers also examined the responses of unhatched chicks to such sounds. They observed a group of birds with three eggs each. They exposed two of the three embryos more than once a day, and for a short time, to distinctive and familiar warning sounds, outside the nest, before they return and place them right next to the third egg in the nest.
The researchers left a group of eggs unexposed to such sounds to test the difference between its response and the response of the other groups.
