Signature Species: What Makes Each County's Wildlife Special? Location Quotients from Open Biological Records

Naturalists have long recorded wildlife by vice county, the fixed recording areas of Britain and Ireland, and the NBN Atlas now publishes hundreds of millions of these records. I ask what makes each county's wildlife distinctive. Using only openly licensed (CC0, CC BY and Open Government Licence) records identified to species, marked present and dated 2000 or later, I count 60,917,118 records of 36,799 species in the 118 vice counties of Great Britain, the Isle of Man and Northern Ireland, and compute for each species a location quotient: its share of a group's records in a county divided by its share of that group's records everywhere. To avoid tiny-sample artefacts I require 20 county records and 200 records in all, and rank species by the lower bound of a 90% Poisson interval. The resulting signature species are recognisable: the corncrake in the Mid Ebudes (175 times its national share of bird records), the Manx shearwater in Pembrokeshire (70), the crested tit in Moray (146) and the mountain ringlet in Mid Perthshire (906). A bird is the signature animal of 45 counties, a mammal of 33 and a butterfly of 26. A chance-corrected distinctiveness index puts the northern isles and the Hebrides at the top and the English Midlands at the bottom. Recording effort varies 25-fold per square kilometre, and the quotients describe records, not populations. Interactive version: https://maps.tristanhotham.com/county-wildlife/. Data and code: https://github.com/Tristan-Hotham/county-wildlife. Blog post: https://blog.tristanhotham.com/2026/10/29/county-wildlife/.