18,000 Bird Species Found On Earth, Twice The Number Previously Estimated

There are about 18,000 bird species found on Earth, a number which is nearly twice of what was previously believed, according to the American Museum of Natural History. The traditional checklists used by scientists and bird watchers generally suggest there are approximately 9,000 to 10,000 bird species in the world.

"This new number says that we haven't been counting and conserving species in the ways we want," said Joel Cracraft, one of the study authors. In general, birds as a species are thought to be a well-studied group. According to a report in The Economic Times, more than 95 percent of bird's global species diversity has been estimated to have been described.

However, such estimates are usually made on the basis of the biological species concept, according to which animals that can breed together are defined as a species. Lead study author George Barrowclough has described biological species concept as an outdated point of view. "It's a concept that is hardly used in taxonomy outside of birds," Barrowclough added, as reported by EurekAlert. "We are proposing a major change to how we count diversity."

The new study focused on the hidden diversity of birds, where birds that look similar to one another and were thought to interbreed to, were different species in reality. The team of researchers conducting the study analyzed a random sample of 200 bird species using morphology. Subsequently, the study of physical characteristics like color and plumage pattern were used to distinguish birds with different evolutionary histories.

With the help of the morphology method, the team found that on an average, there are nearly two separate species for each of the 200 birds examined. According to the researchers, the study indicated that the total number of bird species is likely closer to 18,000 in number, and the earlier count of bird biodiversity was severely underestimated.