How do explorers celebrate Christmas? Hint: It’s on a volcano. Evolutionary biologist and National Geographic grantee Borja Milá and fellow biologist Christophe Thébaud traveled to Réunion, a volcanic island in the southern Indian Ocean, in hopes of figuring out the big evolutionary story behind a tiny species of bird called the Mascarene gray white-eye.
In order to study the birds, the scientists must catch them—or at the least see them. But Mother Nature had other plans for Milá’s team. On Christmas Eve, heavy tropical storms sent birds flying for cover and left the scientists confined to their tent atop the Piton de la Fournaise volcano. Since you won’t catch birds in the rain, the team decided to throw a makeshift Christmas Eve dinner instead. The duck cassoulet looked more like duck mush, and the follow-up course of peanuts from a bag wasn’t much better.
But the explorers kept their spirits high in anticipation of the return of sunshine and dry weather, as Réunion Island is an ideal field laboratory to study the mysteries of evolution. On the nearby island of Mauritius, the Mascarene gray white-eye has only one plumage color form, yet on Réunion Island, which is only about 30 miles long, the bird has evolved into four distinct forms. Each form has a different plumage color, with barriers such as rivers, mountains, and lava flows separating them from each other.
But given that these birds can fly, what is preventing them from crossing the barriers and mating into one mixed form? Will the populations continue to evolve into completely different species? So far Milá, Thébaud, and the team’s research is showing natural selection, sexual selection, and geographical barriers have varying degrees of impact in different regions on the island. As the study continues, the team hopes to answer larger questions about species formation and biodiversity. The scientists will return to Réunion Island in the spring of 2016 to continue their work; you can learn more about Milá’s research on his website.