AviList: A Unified Global Checklist of the World’s Birds is Now Available

Ithaca, NY—AviList, a unified global checklist of birds that provides the most current and authoritative taxonomy of birds around the world, was released today by experts in taxonomy, nomenclature, and bioinformatics including researchers from the Cornell Lab of Ornithology, American Ornithological Society, BirdLife International, International Ornithologists’ Union, and Avibase. The new checklist recognizes 11,131 species of birds in the world, classified within 252 families. 

The AviList team worked for four years to harmonize the global checklist of birds with the aim of providing a single list of species names making it easier to compile and share information on bird species to improve conservation outcomes.

“In trying to protect birds at a global scale, it is important to ensure that everyone is talking the same language and the data match,” said Marshall Iliff, an AviList team member and eBird project leader at the Cornell Lab. Iliff notes that laws and treaties used to protect species don’t work as well when there isn’t consensus on species names.

“If different agencies involved in conservation of biodiversity use different names, then not only is there the chance of misalignment of resources, but also confusion on what needs to be protected,” said ornithologist Les Christidis, dean at Southern Cross University in Australia and member of the AviList team.

“AviList is an exciting leap forward for both birders and conservationists. For those of us involved in bird conservation, species lists are the fundamental units that guide and inform many aspects of our work and an aligned, global taxonomy massively facilitates data analyses, and sets a powerful foundation for our conservation efforts in the field,” said John Mittermeier, director of the Search for Lost Birds Project at American Bird Conservancy, who was not involved in the project. 

The working group of ornithologists and taxonomists behind AviList formed under the International Ornithologists’ Union, with a mission to reconcile the differences in scientific species names among the Clements, International Ornithological Congress, and BirdLife International checklists. The group met monthly to consider questions and classifications across a master list of well over 11,000 potential bird species—pondering and debating over a dizzying array of names, nuances, and spreadsheets.

At its core, the working group sleuths out irregularities much like a detective. “Taxonomy,” said Christidis, “is full of problems that need solving.”

The working group employs an “integrative species concept.” According to Christidis, the integrative species concept “looks at all areas of evidence to make an assessment, including morphology [what a species looks like], behavior, ecology, genetics, phylogenetic relations [species relationships on an evolutionary tree], time since divergence based on genetics, biogeographical distributions, and of course any evidence of reproductive isolation.”

The working group’s debates over species status often go beyond poring through research on evolutionary trees to analyzing sound recordings of breeding songs, inspecting museum specimens for plumage differences, and considering the latest DNA research via genome sequencing. Decisions for the unified checklist are ultimately made by a vote from eight of the working group members.

“It’s work, but it’s fun,” said Pam Rasmussen, one of the Cornell Lab scientists on the working group, who has studied the taxonomy of Asian birds for many decades.

This collaborative effort resulted in a single current consensus taxonomy for the birds of the world, along with key information on taxonomy and nomenclature. The checklist is free to download and can be used by ornithologists, birders, biologists, conservation practitioners, administrators, legislators, and any other stakeholders in bird classification. 

The group behind AviList hopes that a consistent standard for avian taxonomy will reduce confusion arising from incongruent taxonomic sources, make information easier to exchange and aggregate, and clarify species limits for professional and amateur students of birds alike. 

The group’s work will continue, with annual reviews. New scientific research will continue to be published that sheds even more light on the evolutionary relationships of birds, and the birds themselves will keep changing, too.

“Evolution,” said Rasmussen, “is a work in progress.”

AviList Core Team. 2025. AviList: The Global Avian Checklist, v2025. https://doi.org/10.2173/avilist.v2025