These Tiny Birds Became Giants on Remote Scottish Islands

Wrens are among Britain’s smallest birds, but populations living on several remote Scottish islands have followed a remarkably different evolutionary path. New research led by the University of Birmingham found that some have become substantially heavier, genetically distinct and noticeably different in appearance and song.

They are still tiny compared with most birds, so “giants” is relative rather than literal. Yet the transformation is extreme enough to rank among the strongest known examples of island gigantism in birds—and researchers believe some populations may be moving towards becoming separate species.