Grey white-eyes (Zosterops borbonicus) living on Reunion, a small volcanic island in the Mascarene archipelago, have evolved into five distinct color variants associated with separate geographical territories located only 10 kilometers apart, according to a study published on February 27 in Molecular Ecology.

“Birds are usually seen as good dispersers, but these birds stay close to where they are born,” says coauthor Yann Bourgeois, a biologist at the University of Portsmouth in the UK, in a press release. “Based on the results of this study, it’s possible they may be reproducing mostly with birds of the same colour.”

In sequencing the birds’ DNA, Bourgeois and colleagues found that both natural selection occurring from separate physical environments and sexual selection driven by a preference for a mate that looks the same have pushed the birds’ colors apart.

“It’s remarkable that [natural selection and sexual selection] can...

The “highland brown” color variation of the grey white-eye is mostly brown with gray wings.
The “grey head brown” color variation of the grey white-eye is mostly gray but for a ring of brown around its midsection.

Y.X.C. Bourgeois et al., “Differential divergence in autosomes and sex chromosomes is associated with intra-island diversification at a very small spatial scale in a songbird lineage,” Molecular Ecology, doi:10.1111/mec.15396, 2020.

Amy Schleunes is an intern at The Scientist. Email her at

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