Female chickens seem to be able to choose which roosters to make offspring with despite having multiple partners, according to a new study.

Unwanted attention from other comes from socially subordinate males who have developed larger amounts of sperm, in order to pass on their genes, according to the study published in the September issue of the American Naturalist journal.

"We found that hens will eject a greater proportion of the ejaculate from socially subordinate males, so she is in this way favoring the dominant males both before and after ejaculation," said Dr. Rebecca Dean from Oxford University told the BBC.

The tests were carried out on wild hens kept at Stockholm University in Sweden.

"It's really important for females to have the best male sperm to fertilize her eggs, so if she can't choose before copulation, then having a mechanism to choose after copulation could really increase her evolutionary fitness."

The study also said that domesticated hens act similarly, although they have less choice than wild hens, according to the BBC.

The result is similar to Dunnock birds, whose males force their mates to eject sperm from others and protect their own gene pool.