Birds also like the 'petition subject'

Low-grade females will also prefer low-level males, at least in the bird world.

This is a study of Marie-Jeanne Holveck of the Center for Functional and Evolution in Montpellier, France published in the Royal Society magazine. Experimental study on the type of manhole (a species of spiny).

The pair of manholes. Image: Max Planck Institute for Ornithology Previous biologists thought that females would like the best males present around them. But the experiment proved the opposite. Adult females show a preference for songs of males of the same rank.

According to Marie-Jeanne, the low and high-class birds are different in every important characteristic, including the ability to metabolize, longevity and attractiveness.

First, researchers produce low-end and high-end manholes simply by changing their drive size. Marie-Jeanne explains that in larger nests there will be more competition among young birds, which in turn will result in young birds with inferior qualities.

Later, Holveck's team began experimenting with the preference of low-end females to males. The female birds are placed in observable cages, they are trained to peck at two buttons and each time they peck at one, there is a song of a male. A button is a song of a superior male, the other is a male's inferiority.

Professor Holveck said: 'This is an effective test, it tells us what children like to hear.' Low-grade females are constantly pecking at the button with the sound of low-level males and vice versa. For manholes, only males can sing and this is an important erotic signal for females.

In part two of the experiment, Professor Holveck realized that the preference for songs led to real outside attraction.

' Couples with caste often reproduce faster, give eggs faster than other caste couples. The main reason we can come up with is that they are more easily accepted, thus moving faster. The most surprising thing is that the females seem to determine the level they belong to. We will study to explain why they can do that . '

According to Joseph Tobias, a zoologist at Oxford University, this finding is interesting. 'Although it does not reverse the previous thoughts about evolution, it reveals some interesting things about the natural world when considering choice of partners.'

' This shows that the environment in which an individual lives will have a strong influence on that individual's tendency to be attracted to gender '.