The recent study has been performed by Floriane Guibert and Cecilia Houdelier at the CNRS-Universite de Rennes 1 in France, together with researchers at the INRA in Nouzilly, France and with Austrian scientists including Erich Mostl of the University of Veterinary Medicine, Vienna.
It may sound surprising that quails are able to distinguish one another, let alone that they form close relationships with other quails.
Nevertheless, it has long been known that disruption of the birds' social environment causes them stress.
The team of researchers has shown that changing the composition of groups of quails housed together causes the birds to behave more aggressively towards one another. In parallel, the level of steroid hormones (corticosterone) in their blood increases when their group composition is disrupted.
Intriguingly, the eggs they lay were found to have significantly higher levels of testosterone when the mothers were subjected to social stress of this kind.
The results are consistent with previous findings from other groups, which showed that House sparrows, American coots and Common starlings lay eggs with more testosterone when they breed in dense colonies than when they nest in isolation.
But the new work has also shown that the eggs of females under social stress hatch later and the chicks grow more slowly after hatching, at least for the first three weeks.
There are also indications that the chicks' behave differently: they are more cautious and seem more susceptible to disturbance. Furthermore, they tend to move about more, which can be interpreted as increased attempts to escape from threats or to seek more social contact.
The results show how much the growth and behaviour of chicks is influenced by the concentrations of steroid hormones in the eggs from which they hatched.
"We know that stress on female mammals influences the development of their young, which takes place in the womb, but it was a big surprise that social stress causes such changes in the level of hormones in the yolks of birds' eggs," said Mostl.
The social environment of mother quails thus has a direct effect on the growth and the behaviour of their offspring. It seems, then, that pre-natal nurture is extremely important in birds as well as in mammals and this finding is sure to add fresh fuel to the century-old nature versus nurture debate.
The findings were published in the journal PloS ONE.