Barn swallows provide a unique opportunity to explore the speciation process as it unfolds. These birds are one of the most common and widespread species on our planet.

In a new study, scientists describe how different traits used to choose mates in barn swallow populations are driving the bird to diverge, which could eventually lead to the formation of new species.

Over several years, they caught house martins (Delichon urbicum) and barn swallows (Hirundo rustica), analyzed them in terms ...