Stability in their environmental conditions allows them to maintain their singing patterns over the years.
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The "sky island sunbirds" are from the Nectariniidae family and are known for their colorful appearance and nectar diets (similar to hummingbirds). But their history of singing specific songs in the mountains of East Africa is one-of-a-kind, as their singing patterns date back nearly one million years, based on new findings published in the journal Proceedings of the Royal Society B. They appear throughout Africa and Asia and are "little jewels that appear before you," Rauri Bowie, the study's senior author, a professor of integrative biology at the University of California, Berkeley, and a curator in the school's Museum of Vertebrate Zoology, said in a statement.

You can find the birds, formally known as eastern double-collared sunbird (Cinnyris mediocris), in their natural habitat at the peaks of tall mountains in East Africa, such as in Mozambique and Kenya. Researchers wanted to learn more about the birds, and they were particularly interested in determining if the songs they sing have changed throughout the years. They visited 15 different sky islands in East Africa from 2007 to 2011 and recorded songs from the 123 individual sunbirds from six varying lineages.

Greater Double-collared Sunbird
Credit: WitR / Getty Images

The researchers found that some isolated populations of the birds still sing the same songs, which prompted their theory that the songs themselves haven't changed among the lineages that have been apart from one another. They did discover that two populations of this bird that were separated for the longest period of time had songs that were almost the same, but the populations that were together fairly recently sang varying tunes.

Environments that researchers have studied in the past, largely in the Northern Hemisphere, led scientists to believe that birds, and their songs, change frequently based on the change of geological conditions. However, mountains in East Africa have not seen as much change in the environments, which allows sunbirds to maintain their songs over time. "If you isolate humans, their dialects quite often change; you can tell after a while where somebody comes from. And song has been interpreted in that same way," Bowie said. "What our paper shows is that it's not necessarily the case for birds. Even in traits that should be very labile, such as song or plumage, you can have long periods of stasis."

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