The larger and more colourful female greater painted snipe (R) courts males, which look after the offspring Enlarge

A study of shorebirds has helped shed light on why some species reverse the roles of the sexes, with males carrying out the parental duties.

A team of European researchers found that an imbalance between the number of males and females triggered the change.

They reported the switch occurred when there was a higher ration of males to females, making it beneficial for males to stay with their mate.

The findings have been published in the journal Nature Communications.

Adult sex ratio

It had been argued that the conventional sex roles were widespread because females invested considerable energy in producing eggs so the survival of the offspring was a priority, therefore it made sense for the female to oversee the care of the young.

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