This is the red-bellied pitta, a small, insect-eating bird that lives in the Philippines:
But for a long time, scientists believed this other bird, found on Indonesia's Banggai and Sula Islands, was also the red-bellied pitta:
And this little guy, found on a small island off the coast of Papua New Guinea:
But it turns out the birds that were once believed to all belong to the same species—the red-bellied pitta—are actually 13 distinct species, found around Southeast Asia.
This is particularly significant because when they were all lumped together, conservationists weren't worried about their population numbers. But now that the differences have been teased apart, it's become apparent that three of these species are actually globally threatened. One species is also considered near threatened, according to BirdLife International, a bird conservation organization, which is the Red List authority for birds for the International Union for Conservation of Nature.
"The birds do look alike but there are significant differences between individual taxa," explained Nigel Collar, a Leventis Fellow in conservation biology with BirdLife International, who helped to identify the different species.
The first clue came from a team of geneticists who, in 2013, published a paper that showed the red-bellied pitta could be as many as 17 distinct species, based on their genetic diversity. (One factor that can help determine that two animals are separate species is if they are unable to successfully interbreed.) Collar explained that there's a bit of debate over how genetics is used to determine whether a species is distinct, but the evidence convinced him and his colleagues to take a second look at the pitta.
"We sat down in British Museum and got out all the specimen and evaluated these slightly different or fairly different subspecies," Collar said. "So you're comparing the differences: maybe one has a big bill and another has a small bill; a large wing or a short wing."
His team compared the physical differences of each subspecies to every other subspecies, along with data published by Dutch bird researcher Johannes Erritzoe. They then parsed out which birds were actually distinct species using a quantitative criteria that BirdLife International had previously developed called the Tobias criteria—basically a scoring system that makes it easier to measure how distinct two specimen are from one another.
Collar and his team's research, which was published last year in Forktail, a journal on Asian ornithology, determined there was actually 13 distinct species, rather than 17.
This week, when BirdLife International released its 2016 Red List, that research was among lots of other findings resulting in the recognition of 742 new bird species, including the 12 additional pitta species. It also recognized that three of the newly-identified species of pitta—Sangihe Pitta, Talaud Pitta, and Tabar Pitta—are globally threatened, largely due to deforestation.
"The original red-bellied pitta was assessed as being of Least Concern because of its range and numbers," said Alex Dale, digital communications officer for BirdLife International. "But now we know that what we once thought was one species is actually several species scattered across the archipelago, some of which are in danger of extinction. Thanks to this split, we can now identify which of these species are in need of conservation help."