The bird also sounded different, so it was clear that it wasn't from Daphne Major, but its origins were unknown.
Professors Rosemary and Peter Grant of Princeton University collaborated with Prof Leif Andersson of Sweden's Uppsala University to genetically analyze the mixed-species population, and published their findings in Science journal on November 23.
Princeton University scientists B.
Researchers studying the population of finches on Daphne Major, a tiny Galapagos island, found that a population of birds here evolved into new species in a relatively short period of time.
This is the first time that scientists were able to directly observe Speciation, the formation of new and distinct species in the course of evolution in the field.
After decades of hybridisation, a group of finches on the Daphne Major island in the Galapagos Island chain developed closed breeding.
Professor Peter Grant added of the bird that flew in from Espanola: "We didn't see him fly in from over the sea, but we noticed him shortly after he arrived". The team gathered a blood sample. However, these were not able to attract native finches for copulation and thus had to mate within their own new species, making them genetically and reproductively isolated. Cactus finches have bigger body and beak as compared to other finch species living on the island at the time.
"The surprise was that we would expect the hybrid would start to breed with one of the other species on the island and be absorbed", Andersson told the BBC.
The scientist took a sample of blood from the bird before releasing him.
According to the research, the bird mated with a member of another species, resulting in a new lineage that today consists of around 30 individuals. Due to their difference in size and song from the other species, they had no other choice but to reproduce among themselves, thus creating the "Big Bird" species line. Because of this, they mated with their own species. It isn't just the finches though that go through a rapid evolution.
"We have no indication about the long-term survival of the Big Bird lineage, but it has the potential to become a success, and it provides a handsome example of one way in which speciation occurs", said Leif Andersson, a professor at Uppsala University.