The novelty of this study is that we can follow the emergence of new species in the wild.
A new bird species belonging to the Big Bird lineage, which today consists of roughly 30 individuals, emerged on the Galapagos Islands in just two generations, according to a study.
Researchers previously assumed that the formation of a new species took a very long time, but in the Big Bird lineage it happened very soon.
The new species of Darwin's finch was observed during field work carried out over the last four decades by B Rosemary and Peter Grant, two scientists from the Princeton University in the US, on the small island of Daphne Major.
All 18 species of Darwin's finches derived from a single ancestral species that colonised the Galapagos about one to two million years ago.
In 1981, researchers noticed the newcomer, a male that sang an unusual song and was much larger in body and beak size than the three resident species of birds on the island.
"We didn't see him fly in from over the sea, but we noticed him shortly after he arrived. He was so different from the other birds that we knew he did not hatch from an egg on Daphne Major," said Peter Grant.
They took a blood sample and released the bird, which later bred with a resident medium ground finch of the species Geospiz fortis, initiating a new lineage.
This gave rise to a new species that today consists of roughly 30 individuals, according to the study published in the journal Science.
The team followed the new "Big Bird lineage" for six generations, taking blood samples for use in genetic analysis.
Scientists from Uppsala University analysed DNA collected from the parent birds and their offspring over the years.
"The novelty of this study is that we can follow the emergence of new species in the wild," said B Rosemary Grant.
"Through our work on Daphne Major, we were able to observe the pairing up of two birds from different species and then follow what happened to see how speciation occurred," she said.
The breeding of two distinct parent species gave rise to a new lineage (termed "Big Bird" by the researchers). This lineage has been determined to be a new species.