These sunbirds keep singin’ their song

Sky-island populations of East African double-collared sunbirds have been isolated from one another for hundreds of thousands if not a million years, but still look very similar. While almost indistinguishable in plumage, however, some of these bird lineages have altered their songs a lot while others have not — their songs differ little from the songs of related populations they’ve not encountered for millennia. A new study by biologists from the University of California, Berkeley, and Missouri State University in Springfield, however, documents songs in East African sunbirds that have remained nearly unchanged for more than 500,000 years, and perhaps for as long as 1 million years, making the songs nearly indistinguishable from those of relatives from which they’ve long been separated. The amazingly static nature of their songs may be due to a lack of change in these birds’ environments, which are stable mountain forests — so-called sky islands — isolated from other sky island populations of the same or