Sparrows can choose gender for their children

After sharing the roof with a bad guy, most of the eggs in their nests will hatch into males.

A rainbow flock in Australia.Photo: angelo.edu.

In most birds on the planet, the sex of an egg is decided before the male is fertilized. But Sarah Pryke, a biologist at Macquarie University (Australia), said the females of the rainbow fin (Chloebia gouldiae) could change the sex of the young bird. She noticed that when the female mate with the male is not suitable, 70% of the eggs will hatch into males.

Rainbow bridges live in areas near water, forest cover in northern and central Australia. People call them rainbow because their fur is colorful. All rainbows have purple feathers in their breasts, so they are called purple chests. The length of the adult body is about 12-14 cm.

Rainbow hair on the head is black, red and yellow, of which black heads account for about 75%. Females can recognize the genetically appropriate drum by looking at the head. If the color on the head of the drum coincides with the color on the head of the female, they are a suitable pair. Mating with males has the same color on the head to help females lay out healthy babies. In that case, the number of males and females in the nest will be equal.

'Sharing roofs do not want to mate with males whose hair color is different from theirs. But many cannot find drums of the same color on their heads. Therefore, when spawning, they must use measures to increase the number of males to minimize the risk of young birds , 'Pryke said.

Black heads accounted for 75% of the total number of rainbow visits, while only a few thousand each owned a yellow head.Photo: angelo.edu.

To prove that female finches can control the sex of young birds, Dr. Pryke and colleagues try to trick the female. They picked a few red heads and blackened the hair on their heads. The team then locked them in cages with red heads and black heads.

'Sharing the roof does not recognize the true color of the male's head hair. They are completely fooled, ' Pryke said. The results showed that when the black-headed female mates with fake black-headed males, the ratio of male and female in the nest is equal. In the red-headed bird's nest, the number of young males accounts for 70% even though it is mated with a male with the same head color.

'This is the clearest and most convincing evidence of gender bias in birds,' Pryke said. However, the way birds control the sex of eggs is still a mystery. 'We think hormones may play a role, but this hypothesis needs to be verified,' Pryke said.