TORONTO -- In a monumental effort, Australian researchers have attempted to estimate how many birds there are in the world using observation data from more than 600,000 citizen scientists. According to the research, published in the Proceedings of the National Academy of Sciences on Tuesday, there are approximately 50 billion individual birds in the world – or about six birds for every human on the planet. “Humans have spent a great deal of effort counting the members of our own species - all 7.8 billion of us,” Will Cornwell, an ecologist at University of New South Wales Science and co-senior author of the study, said in a press release.