The Number of Bird Species Could Be Double What We Thought

Our feathered friends have been taxonomically shortchanged, a new study argues.

There could be twice as many bird species as we thought.

So say researchers from the American Museum of Natural History, who argue in a new study published in the journal PLOS ONE that birds have been greatly underrepresented, taxonomically speaking.

Typical numbers for the total number of bird species worldwide tend to center around a range of 9,000 to 10,000, but the museum's scientists say that number is likely closer to 18,000.

Of course, that begs the question: How could science be so far off? The researchers say it's all about how birds have been placed in various species. Bird species counts, they say, center around an idea known as the "biological species concept," in which species are defined based on which animals breed together.

"It's really an outdated point of view," said the study's lead author George Barrowclough in a statement, "and it's a concept that is hardly used in taxonomy outside of birds."

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Barrowclough and his colleagues used different metrics to assign species, based instead on physical characteristics such as plumage and color. They studied a random sampling of 200 species through that framework and discovered that within that group there were almost two new species for each bird they examined.

Extending that ratio out to the entire bird population, the researchers suggest that there may be roughly double the number of bird species in the sky.

Going forward, the scientist say bird species assessments should take into account physical characteristics as well as genetic data.

The counts matter, they say, because individual species are the benchmark used in conservation. "We really need to be clear about what a species is, how many there are, and where they're found," said study co-author Robert Zink.

"This new number says that we haven't been counting and conserving species in the ways we want," added co-author Joel Cracraft.

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