Love birds glow crazy

Research is not a flight of fancy

Budgies have fluorescent plumage which sends out a strong sexual signal to would-be partners, researchers have found.

Scientists found that budgerigars are attracted to potential mates whose feathers give out a glow of sexual radiance.

The researchers, led by Kathryn Arnold from Glasgow University, UK, said that to a budgie the head of a potential suitor could appear to be lit up like a gorgeous beacon.

They demonstrated the fact in an experiment in which budgies had their heads daubed with sunblock.

A scientist from Glasgow University led the team

Fluorescent pigments, like those used in highlighter pens, appear to glow when they absorb ultraviolet light and re-emit it at longer wavelengths.

In budgies, both sexes have fluorescent yellow plumage on their crown and cheeks that is used in courtship displays. The scientists showed that the fluorescence is no accident.

It is there for the express purpose of demonstrating an individual's sex appeal.

Budgie eyesight

Writing in the journal Science, the researchers described how they applied sunscreen to the yellow crown feathers of male and female budgies to reduce their UV absorption.

Both showed a clear preference for members of the opposite sex whose fluorescence had not been dulled.

The scientists were able to calculate the effect of fluorescence, as perceived by another budgie.

Taking into account the light sensitivity of budgie eyesight, they found that fluorescent plumage adds 14% more "chromatic signal" to the crown region.

"These findings show that the fluorescent plumage of parrots is an adapted sexual signal, rather than a by-product of plumage pigmentation," wrote the researchers.

Since it took elaborate biochemistry to produce fluorescent pigments, they may provide "honest indicators of individual quality", they added.