A new study helps reveal why tropical mountain birds occupy such narrow elevation ranges, a mystery that has puzzled scientists for centuries. While many assumed temperature was responsible for these limited distributions, ...
The study, conducted by researchers at the University of British Columbia and the Cornell Lab of Ornithology, incorporated 4.4 million citizen science observations of 2,879 bird species around the world. The findings were published in Science on July 21.
"You have this incredible biodiversity in mountain ranges, especially in the tropics. From one vista point in the Andes, you can see a mountain slope that's home to as many species as there are in the entirety of North America," said lead author Benjamin Freeman, a postdoctoral fellow at the University of British Columbia. "We wanted to know, how does that work?"
Freeman and his collaborators obtained the range data by analyzing records from eBird, a citizen science project run by the Cornell Lab that contains sightings from hundreds of thousands of birdwatchers worldwide. This enabled them to examine the ranges of over a quarter of the world's bird species scattered over five continents—a scale unimaginable to past researchers.
"Aside from eBird, you just have really coarse range maps, especially on a global scale," said co-author Eliot Miller at the Cornell Lab. "The eBird database is uniquely broad in both space and time, giving us more insight into bird distribution around the world than we have for any other organisms."