What is an endemic? The taxonomic position of at least the British birds listed below has been under discussion for decades, and is now in urgent need of review given that we are in a situation where one taxon, Scottish Crossbill, can be and is treated as a species by some authorities (e.g. IOC) but as a subspecies by others (e.g. Shirihai & Svensson), whilst several formerly recognised subspecies are no longer recognised by either IOC or Shirihai & Svensson.
In the past new subspecies were sometimes named on tenuous grounds, but it is also fair to say that some recent deletions have been a little arbitrary. An authoritative review would need to look at a wide range of museum material, photographs, sound recordings, and genetic material. It is perhaps surprising that this hasn’t been done already.
The species (in addition to Scottish Crossbill) for which endemic or near-endemic British taxa are currently recognised by IOC are: Red Grouse, Ptarmigan, Black Grouse, Lesser Black-backed Gull, Herring Gull, Guillemot, Great Spotted Woodpecker, Lesser Spotted Woodpecker, Rock Pipit, Yellow Wagtail, Pied Wagtail, Dipper, Wren, Dunnock, Robin, Stonechat, Song Thrush, Long-tailed Tit, Blue Tit, Great Tit, Crested Tit, Coal Tit, Willow Tit, Marsh Tit, Treecreeper, Jay, Starling, Chaffinch, Goldfinch, Linnet, Twite, Bullfinch, and Yellowhammer.