They say that beauty is in the eye of the beholder. For male rainbow finches, that’s definitely right. As in right eye. The birds depend on their right eye for scoping out potential mates.

Many males are choosy when picking a partner. And the rainbow, or Gouldian, finch is no exception. Songbirds with colorful and variable plumage, Gouldian males tend to go for a gal with a pretty face, one that pretty much matches his. So males with black faces prefer females with the same. But that bias, it turns out, depends on how they look at her.

Researchers gave black-faced male finches a choice: they could flirt with black-faced females, red-faced females or a fellow male. Males with both eyes open cozied up to the doll with the dark feathers. But when researchers covered the males’ right eye, the males sang and danced with everyone, or hopped around randomly looking lost. You can use either eye to see the finding in the journal Biology Letters. [Jennifer J. Templeton et al., In the eye of the beholder: visual mate choice lateralization in a polymorphic songbird]

The right eye feeds info to the left half of the brain. And so it seems, males that are really particular when it comes to choosing a partner are not in their right minds.

—Karen Hopkin

[The above text is a transcript of this podcast.]