This is bird note. Sometimes birds change their tune. For example, white-throated sparrows in many areas have shortened their songs in just a few decades.

But there are also songs that appear to have stayed the same over millennia.

Several related species of sunbirds in eastern Africa live on isolated mountaintops, also known as Sky Islands.

Their mountaintop habitats led them to become distinct populations

and, in some cases, evolve into different species. But researchers found that two populations

of one species, the forest double-collared sunbird still have nearly identical songs, despite

having separated into different mountains at least 500,000 years ago. That suggests the song

that these sunbirds sing today is probably very similar to that of their long lost ancestors.

The findings show that there are good reasons for a species to keep singing the same old song.

Having a unique and stable song helps birds recognize members of their own species,

even if their ancestors split up long ago.

So, if a tune works, don't change it.

For Bird Note, I'm Michael Stein.