How we write and check
We write from published sources, show them on the page, and fix mistakes when you tell us
Where the facts come from
We write from published sources: field guides, the scientific literature, and the organisations that count and study birds, such as BirdLife International and the IUCN Red List, the British Trust for Ornithology and the Cornell Lab of Ornithology.
Species pages list their sources at the end, with what each one was used for. Bird facts name their source under the fact.
Sizes, weights and lifespans
Measurements come from our species data, which records each figure once. Where a page’s text and the data disagree, we treat it as a mistake and fix the text.
Lengths are bill to tail; weights are typical adult ranges; “oldest recorded” ages come from ringing records.
Where and when birds are seen
Our lists of the birds in each country, county and state, and the month-by-month charts, are built from the eBird Observation Dataset (Cornell Lab of Ornithology), shared through GBIF under a CC BY 4.0 licence.
A bird is listed for a place when it is recorded there in at least three of the six years. Records follow birdwatchers as well as birds, so a busy month can mean more people out looking.
How we check
Every article and species guide is checked by Nathan Cope, Birdfact’s founder and editor, before it’s published. Our articles are researched and written by Birdfact’s writers and contributors in the UK, the US and Canada; Nathan has watched and studied birds for more than ten years and writes for the site too.
Each page says who checked it, and shows when it was last updated.
How we use AI
The bird identifier is Birdfact’s own identification service. It uses AI image and sound recognition, weighs the answer against the birds recorded where and when you saw yours, and matches it to our species guides. It tells you how sure it is, in words, and shows you the bird it might be confused with.
We also use AI tools to help draft and check some short species summaries. A person decides what is published.
Photos
Our photos are licensed from photo libraries. Captions say what the photo shows, and the same words describe it for people using screen readers.
Adverts
Articles carry adverts, which pay for the site. Advertisers don’t choose or pay for what we write. Birdfact Unlimited members see no adverts.
Spotted a mistake?
Please tell us, with the page and what is wrong. We check it against the sources, fix it, and update the page’s date.