Some East African birds have been singing the same song for hundreds of thousands of years
Scientists were able to establish this through field research.
A new study by biologists from the University of California at Berkeley and the University of Missouri at Springfield documents the songs of East African Cinnyris sunbirds that have hardly changed for more than 500,000 years, and possibly even a million years. Their songs are almost indistinguishable from the songs of relatives from whom they have long been separated.
The surprisingly static nature of their songs may be due to the lack of change in these birds’ habitats, which are persistent montane forests isolated from other populations of the same or similar species for tens of thousands of years or more. The coloration of the birds’ feathers has also changed little, making their plumage almost indistinguishable from each other, although some are separate but closely related species.
“If you isolate people, their dialects change quite often; you will be able to tell after a while where someone came from. And the songs were interpreted in the same way. Our work shows that this does not necessarily apply to birds. Even traits that should be highly labile, such as singing or plumage, can have long periods of stagnation,” Rauri Bowie, lead author of the study.
Bowie says the idea that birdsong changes easily probably came from studies of Northern Hemisphere birds, which have repeatedly experienced changing environmental conditions as glaciers have come and gone over the past tens of thousands of years. Environmental change causes changes in plumage, birdsong, mating behavior and more.
But the mountaintop environment in the tropics, especially in East Africa—from Mount Kenya to Mount Kilimanjaro in southern Tanzania through Malawi to Mozambique—has undergone little geological change over the same time period. Thus, the birds studied by the researchers had no incentive to change either their colorful plumage or their often intricate songs.
“Song is considered to be one of the most important insulating barriers before mating, one of the key ways birds tell each other apart. The fact that the trait we have studied can remain unchanged for hundreds and thousands of years is simply remarkable. This discovery reflects how much the field study of tropical systems has to offer the scientific community and the curious observer.” – Rauri Bowie
Bowie, along with colleague Jay McEntee, began their research almost 15 years ago. Between 2007 and 2011 they recorded the songs of 123 individual birds from six different bloodlines of East African sunbirds.
The researchers developed a statistical method to distinguish between gradual changes and bursts of rapid change in traits such as bird song, and found that song differences do not appear to correlate with how long individual populations have been separated, as estimated based on genetic data. differences in their DNA. In particular, two populations of long-separated species had nearly identical songs, while two other similar species that had been separated for less time had very different songs.
“What surprised me the most in doing this study was how similar these learned songs of isolated populations within species were, and how obvious were the differences in songs where they were found.
When we recorded the song Cinnyris Fuelleborni, which we call the Füleborn sun bird, we thought that there must be another bird nearby that sang at the same time. We looked directly at the singing bird, watched it move its beak, and could not believe how different its song was from the very similar-looking Moro sun bird, Cinnyris moreaui, which we had just recorded elsewhere,” says McEntee.
On the other hand, the songs of Cinnyris Fuelleborni from the Ikokoto populations in Tanzania and the Namuli populations in Mozambique are almost identical despite being separated by hundreds of kilometers and hundreds of thousands of years.
Based on this study, biologists argue that characteristics such as learned song and plumage do not drift in isolated populations. On the contrary, they develop in impulses, remaining with small changes for a long period. Sometimes hundreds of thousands of years.