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Male birds lose interest in fading females

Wandering eye Male blue tits lose interest when their mates' beauty starts fading, staying out longer and neglecting their offspring, a new study has found.

Scientists who dulled the bright blue head tinge that crowns the female of the species, subsequently noticed the males skulking off for more alone time and making fewer trips to feed their chicks.

"It seems that they stay around, but not in the nest," says study co-author Matteo Griggio of Konrad Lorenz Institute of Ethology in Vienna.

"Probably they take a rest ... It is not a joke, probably they keep some energy, maybe for the next breeding season?"

Both male and female blue tits (Cyanistes caeruleus), which usually have several mating partners in a lifetime, have feathers on the tops of their heads that reflect UV light.

For the purposes of the experiment, the team waited for chicks to hatch before smearing an oil containing UV-blocking chemicals on the crowns of the females.

To confirm that it would not be the smell that put off the males, they applied the same oil, without UV-blockers, to a separate test group of females.

The scientists say they took care not to render the partners unrecognisable to each other.

"The UV reflectance of the crown plumage of female blue tits significantly affected male investment in feeding nestlings," the team write in a study to be published in the BioMed Central journal Frontiers in Zoology.

"Males made less frequent feeding trips when paired with UV-reduced females."

While much has been written about male posturing and strutting to compete for female attention, this was a rare study to measure male response to female attractiveness in the animal kingdom.

The results showed that female blue tits must invest a lot of time in preening to remain attractive as sexual partners.

In nature, those birds with poorer personal hygiene risk losing their blue lustre under a coating of dust, pollution or parasites.