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Cheating Fairywrens

October 28, 2013

Female fairy wrens are more likely to cheat with males that have red plumage.



Scarlet letter birds. I’m Bob Hirshon and this is Science Update.

An orange-backed male (right) and an orange-backed male artificially tinted red (left). (© Daniel Baldassarre)

Australian Red-backed Fairywrens form long-term pair bonds to raise families. But both sexes also sneak off to mate with their neighbors, according to Cornell behavioral ecologist Dan Baldassarre.

DAN BALDASSARRE (Cornell University):

And so if you do genetic testing, sort of like a Jerry Springer paternity test type of situation, you find out that a lot of those offspring are coming from males other than the dad who’s there taking care of them.


Baldassarre says males of the species come in two varieties, bright red and flame orange. But lately, red birds have been observed in areas previously occupied only by orange birds. So he and his team used art markers to artificially turn orange males red. They found that females were much more likely to cheat with red males than oranges ones. The researchers are now trying to figure out what makes red males so irresistibly sexy. I’m Bob Hirshon, for AAAS, the science society.

The scarlet-backed form (left) and orange-backed form (right) of the Red-backed Fairywren overlap in a small region of northern Queensland, Australia. The scarlet-backed form is steadily extending its range into the orange-backed's range—a pattern apparently driven largely by the preferences of females mating outside their pair bond. The dot indicates where the plumage coloration experiment was performed. (Fairywren images © Tom Tarrant (left) and © Tim Laman (right)