eBird: How Birdwatchers’ Sightings Became a Global Science Tool

eBird is a free online database of bird sightings, run by the Cornell Lab of Ornithology at Cornell University, to which anyone can submit what they see and hear. By mid-2025 it held two billion bird observations from 1.1 million contributors in 253 countries, and scientists use it to study migration, population trends and habitat needs, the Lab reports.

History of eBird

eBird was launched in 2002 by the Cornell Lab of Ornithology and the National Audubon Society, according to its primary scientific description, published in 2009 in the journal Biological Conservation. That paper described eBird as a tool for birders at its most basic level and as a tool for science and conservation at its highest level. Most early users were in the United States and Canada, the Cornell Chronicle notes, before the program spread to Mexico and then worldwide.

Growth has sped up. The Lab says it took 19 years to reach the first billion observations, in 2021, and only four years to reach the second, helped by submissions from 51 additional countries. By August 2025 eBird supported 99 languages and worked with hundreds of partner organizations across every continent, according to the Cornell Chronicle.

How eBird works

The basic unit is the checklist, a record of the birds a person saw or heard on one outing. Contributors need a free Cornell Lab account. Complete checklists, which list every species the observer could identify and report the search effort, are the most valuable, according to the Lab. They let researchers infer which species were not detected, so a species that was not seen can be recorded with a count of zero rather than treated as missing.

Short checklists are better than long ones, the Lab advises, because a long checklist over a large area says less about exactly where and when each bird was seen. Thousands of data quality volunteers help keep the records reliable, and researchers can request the full raw dataset free for noncommercial use under eBird’s terms.

What eBird data is used for

Researchers had used eBird data in more than 1,250 published studies as of August 2025. One, published in Science in May 2025, used 36 million eBird observations to conclude that bird populations in North America are declining most in the areas where they have historically thrived, the Cornell Chronicle reports.

The Lab also turns the records into tools. eBird Status and Trends uses statistical models and machine learning to estimate where bird populations occur and how they change over time, with updates every year. Its Trends maps show where birds have been increasing or decreasing since 2012 within areas of 27 by 27 kilometers, the Lab says.

The BirdCast migration dashboard and the Merlin Sound ID feature draw on the same data, and national and international efforts such as the Africa Bird Atlas Project use it too. The Lab also credits the records with supporting studies of plumage aberrations and the spread of exotic species, habitat restoration work and efforts to reduce disease transmission.

A University of St Andrews ecologist quoted by the Lab says the dataset is improving scientists’ ability to respond to the global biodiversity crisis.

Advantages and disadvantages of eBird

The main advantage is scale. The Lab says eBirders provide data at a scale scientists could not reach alone, and the records arrive in near real time.

The main disadvantage is uneven coverage. Contributors choose where and when to watch, so the Lab describes the data as semi-structured, and researchers rely on complete checklists and statistical models to account for the gaps. A Cornell Lab coordinator for Latin America says the region has been under-represented despite its rich bird life, and that eBird now helps local groups monitor species and migratory movements. A June 2026 Cornell release adds that its new migration method could expand worldwide only where there is adequate citizen science data.

Why eBird is getting attention now

Several developments point the same way. In June 2025, eBird passed two billion observations. The two-billionth was a tropical kingbird reported from Honduras, and as of August 2025 the Lab projected three billion within two years.

In March 2026, the Cornell Lab and the UN Convention on the Conservation of Migratory Species of Wild Animals launched the Americas Flyways Atlas at a UN meeting in Campo Grande, Brazil. Built on many millions of eBird observations, the tool maps the annual routes of an initial 89 vulnerable migratory bird species across 56 countries. It marks Bird Concentration Areas, places where large numbers of listed species gather at different stages of migration, and it aims to help governments decide where habitat protection matters most.

The release says 622 migratory bird species in the Americas depend on a chain of habitats, and many are in decline under pressure from habitat loss, infrastructure and climate change.

In June 2026, researchers at the Cornell Lab, the University of Massachusetts and the University of Illinois reported two papers that combine eBird data with weather radar. Radar detects how many birds are flying overhead but not which species, so the new BirdFlow methods estimate species-specific migration for 153 North American species. The team checked its estimates against 28 years of data from 152 weather radars and against GPS-tracked birds, and says the models could also help monitor avian influenza routes and reduce window collisions.

FAQs

Is eBird free?

Yes. Contributors need a free Cornell Lab account, and raw data is free for noncommercial use on request.

Who runs eBird?

The Cornell Lab of Ornithology runs it. It was launched with the National Audubon Society in 2002.

Does eBird cover Africa?

eBird has data from 253 countries, and the Lab lists the Africa Bird Atlas Project among the efforts that use it.