The world has about 50 billion individual wild birds, according to a new, first-of-its-kind study — suggesting that there are six times as many birds on the planet as humans.

“It’s really ambitious — it’s a big undertaking to try and figure out how many birds there are in the world,” Lucas DeGroote, a researcher at the Carnegie Museum of Natural History’s Powdermill Avian Research Center in the U.S., who wasn’t involved in the study, told National Geographic.

Scientists have drawn rough estimates of the global bird population in the past, concluding there may be about 200 to 400 billion birds in the wild. But this is the first attempt to quantify them in a more tangible, data-backed manner. Moreover, identifying the population sizes of different bird species will boost efforts to protect them, scientists note.

The figure of 50 billion includes 9,700 identified species of birds — including even flightless ones like emus, kiwis, and penguins. Published in Proceedings of the National Academy of Sciences, the study used two observations: one made by almost 600,000 citizen scientists — members of the civil society who are also bird-watchers — to estimate the populations of about 10,000 bird species; the other by professional scientists. In order to ensure greater accuracy and minimize the margin of error, the researchers cross-checked the results for some species with other data sources.

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“The really big breakthrough in this paper was we could take the scientific data and the citizen science data and then fill the gap for birds which are not studied by professional scientists,” Will Cornwell, an ecologist at the University of New South Wales in Australia, who was involved in the study, told The Guardian. “The whole idea came from the fact that there are a few bird species that get really, really well studied. But there is this huge collection of citizen scientists traveling all over the world counting every bird that they see,” he added.

Experts believe this study is an important milestone in avian conservation. “By properly counting what’s out there, we learn what species might be vulnerable and can track how these patterns change over time — in other words, we can better understand our baselines,” Corey Callaghan, a biologist at the German Center for Integrative Biodiversity Research, who co-authored the study, said in a statement. “Quantifying the abundance of a species is a crucial first step in conservation.”

However, only four species of birds were found to have billion-plus populations — house sparrows were the most dominant among them with a population of about 1.6 billion. On the other hand, more than 1,000 species had fewer than 5,000 birds each. According to scientists, this disparity could inspire investigations into why only a handful of bird species evolve to become so dominant.

Researchers also believe the contribution of this study extends beyond the conservation of avian creatures — this model of combining professional and citizen-science data can, perhaps, allow scientists to undertake similar ventures for other animals as well. “While this study focuses on birds, our large-scale data integration approach could act as a blueprint for calculating species-specific abundances for other groups of animals,” Callaghan noted.