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Researchers call for changes to avian ‘taxonomy anarchy’

taxonomy anarchy
Augur Buzzard (Buteo augur) in Tanzania. Photo by Rini Kools/Shutterstock

How many raptor species exist on planet Earth? If you look at the four most widely used lists of recognized bird species, you’ll get four different answers.

The Howard and Moore Checklist of the Birds of the World lists 528 raptors (hawks, eagles, kites, vultures, falcons, caracaras, owls, and seriemas). The eBird/Clements Checklist of Birds of the World records 561. The Handbook of the Birds of the World/BirdLife International list has 567, and the International Ornithological Community World Bird List contains 580 raptors.

This broad discrepancy is a problem, especially for bird conservation, says Chris McClure, director of global conservation science at The Peregrine Fund.

Altogether, the four lists count 665 species-level raptor taxa at least once, only 453 of which (68 percent) are consistent across all four lists. Of the disagreements, 67 percent involve owls, and Indonesia was the country containing the most disagreed-upon species (169). The variations among the lists “lead to confusion among conservation practitioners and government agencies,” McClure says.

An example is the bird pictured above, Augur Buzzard (Buteo augur), a hawk found in eastern and southwestern Africa. The eBird/Clements and IOC lists consider it separate from Archer’s Buzzard (B. archeri), of Somalia, but the Howard and Moore and Handbook/BirdLife lists consider Archers Buzzard to be a color morph of the Augur Buzzard.


The checklists all have different origins and are used for different purposes. The IOC list is used by the international ornithological journal Ibis. The Howard and Moore Checklist is used by several major museums around the world. The eBird/Clements Checklist is used by the Cornell Lab of Ornithology in the implementation of its programs, including eBird. And the Handbook of the Birds of the World/BirdLife list is followed by BirdLife International when determining the Red List of Threatened Species and for several international agreements.

“If this all sounds a bit confusing, that’s because it is,” McClure adds. “In fact, the differences between the four world bird lists were recently referred to as ‘taxonomy anarchy.’”

In June, McClure and colleagues from Birds Canada, the Cornell Lab of Ornithology, and four universities published a paper in Proceedings of the Royal Society B calling for the four lists to be reconciled into a single authoritative list of the world’s birds.


“The bottom line is that, if we want to conserve birds, including raptors, working together to develop a single world bird list would go a long way,” says Denis Lepage of Birds Canada.  According to McClure, efforts are now being discussed to consolidate the four lists, but no official announcement has been made concerning when that may happen.

“Oftentimes, taxonomic research is not well funded,” adds Lepage, “but this study demonstrates that a concerted effort is critical for conservation of biodiversity. This is too important to not give our best effort.”

In early August, the International Ornithologists’ Union announced it will build a consolidated Global Checklist. This list will use the IOC World Bird List as its template, and “will be an independent benchmark work with broader taxonomic coverage compiled by the IOU teams, which include the IOC World Bird List co-editors.” The IOU has established a working group for the new Global Checklist that includes some of the co-authors of McClure’s recent paper, including Marshall Iliff of eBird and Denis Lepage, the creator of Avibase.


This article first appeared in the September/October 2020 issue of BirdWatching magazine. 

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