Scottish wrens may be evolving into new species through island gigantism

Tiny birds on remote Scottish islands are undergoing a dramatic evolutionary transformation. Scientists studying four isolated populations of British Wrens discovered that some island birds have grown astonishingly large — with the biggest St Kilda Wrens weighing more than twice as much as the smallest mainland birds. The research suggests these wrens are evolving independently, developing unique songs, appearances, and genetics that may eventually turn them into entirely new species.