For every human being on Earth, there are approximately six birds: some unable to take flight, others capable of soaring through the air, some endangered, and others with large populations. These estimates were published in the Proceedings of the National Academy of Sciences, crafted by scientists from the University of New South Wales (UNSW), who utilized data obtained from observations made by citizens.
The team developed an algorithm to calculate the number of individuals belonging to each of the 9,700 different bird species. Researchers collected nearly a billion bird sightings recorded on eBird, an online database dedicated to birdwatchers. From emus to penguins to cockatoos, the authors discovered that there could be more than 50 billion birds currently on the planet. Scientists highlight that some endemic species in Australia, such as Swainson’s Lorikeet, have over 19 million individuals, while others, like the Black-breasted Buttonquail, seem to be heading towards possible extinction, with around 100 specimens remaining in the area.
“Several efforts have been made to count each of the 7.8 billion human beings,” says Will Cornwell, an ecologist at UNSW and co-author of the paper. “This is the first attempt to comprehensively enumerate another class.”
“Although our work focuses on birds,” notes Corey Callaghan, the lead author of the article, “this large-scale data integration approach could serve as a model for calculating species-specific populations for other animal groups.” Quantifying the presence of a species, experts emphasize, is a fundamental first step for its conservation. Among the most populous species on the planet, researchers identify the domestic sparrow at the top of the list, with a total of 1.6 billion individuals, followed by the European starling (1.3 billion), the American gull (1.2 billion), and the common swallow, with 1.1 billion units.