The findings were announced in a study published in the Proceedings of the National Academy of Sciences.
There are about 50 billion wild birds in the world today. That means birds in the wild, birds on the street, birds outside my window waking me up every goddamned morning.
Researchers were looking into avian populations for conservation purposes and used the bird sightings of 600,000 contributors to eBird, a community of citizen scientists and birders. These sitings form the basis of the team's big-data approach. The plan is to repeat the studies every few years to keep tabs on avian life. “We will need to repeat and refine this effort to really keep tabs on biodiversity—especially as human-caused changes to the world continue and intensify,” said Dr. Corey Callaghan, co-author of the study.
The findings, which were published in The Proceedings of the National Academy of Sciences, has some issues. Birdwatchers are more likely to report certain species. For this reason, when making species-specific estimates, the researchers included a “detectability” factor. Despite some uncertainty in the estimates, they are incredibly comprehensive and include figures for 9,700 bird species (92 percent of all avian species on the planet).
Some of the findings have helped identify birds in danger. The Chinese Crested Tern, Noisy Scrub-bird, and Invisible Rail are among the 12 percent of species with populations under 5,000. Others are thriving. The House Sparrow (1.6 billion), European Starling (1.3 billion), Ring-billed Gull (1.2 billion), and Barn Swallow (1.1 billion) are the only four species to exceed one billion estimated individuals. Co-author and Associate Professor Will Cornwell says that for any species, “if their population numbers are going down, it could be a real alarm bell for the health of our ecosystem.”