Kathryn Arnold of the University of Glasgow led a research team that found the fluorescent yellow feathers on budgies' heads play a vital role in attracting mates.
The team found male and female budgerigars preferred brighter plumage when choosing a mate, after using odorless sunscreen to dim fluorescent feathers' on some of the birds that were studied.
When the birds were exposed to the same sex, the level of fluorescence did not distract from social interaction.
The researchers concluded that fluorescence contributes to attracting sexual partners.
Arnold's findings may apply to other birds, as she has examined more than 60 species and discovered most of the feathers that were found to be fluorescent are used in courtship displays.
Arnold's findings were published in the January 4 issue of Science.