New Delhi: As per a latest report, the number of bird species in the world has rose to 18,000- nearly twice as previously thought.
"This new number says that we haven`t been counting and conserving species in the ways we want," said one of the study authors, Joel Cracraft, from American Museum of Natural History.
Birds are traditionally thought of as a well-studied group, with more than 95 per cent of their global species diversity estimated to have been described.
Most checklists used by bird watchers as well as by scientists say that there are roughly between 9,000 and 10,000 species of birds.
But those numbers are based on what is known as the "biological species concept," which defines species in terms of what animals can breed together.