With the BOU's adoption of the IOC taxonomy from 2018 the following changes will occur.

Bean Goose becomes two species; Taiga Bean Goose and Tundra Bean Goose. Previously these were races of the same species.

Fea's / Desertas Petrel becomes two species though this does not affect the list total since only one of the taxa (presumably) has occurred. In fact, if the actual species cannot be determined, then presumably the species will have to be removed from the British List

Isabelline / Red-tailed Shrike becomes two species. Previously these were races of the same species.

Little / Least Tern becomes two species. Previously these were races of the same species.

Greenish / Two-barred Warbler becomes two species, Previously these were races of the same species.

Siberian / Stejneger's Stonechat becomes two species. Previously these were races of the same species.

Eastern / Western Yellow Wagtail becomes two species. Previously these were races of the same species.

Hudsonian Whimbrel and Whimbrel become one species. Previously these were considered two species but "Hudsonian" Whimbrel is now a race of Whimbrel and becomes Numenius phaeopus hudsonicus.

The IOC made changes in July 2017: Thayer's Gull had been a separate species (now a race of Iceland Gull) and Lesser Redpoll which hade been a race of Common Redpoll is now a species.

IOC British list total now 613.

Recent changes

Western Swamphen Porphyrio porphyrio

August 2017: Added to Category A of the British List.

Red-footed Booby Sula sula

August 2017: Added to Category A of the British List.

Eastern Kingbird Tyrannus tyrannus

August 2017: Added to Category A of the British List.

Pale-legged Leaf Warbler Phylloscopus tenellipes

August 2017: Added to Category A of the British List.

Elegant Tern Thalasseus elegans

A colour-ringed bird of proven identity via an innovatory DNA analysis was found in Hampshire in June 2017 and again later in West Sussex. Given that its identity and provenance is indisputable, it will inevitably be accepted by both BBRC and BOU. However, it may not become the first accepted record as two other birds from Devon/Caerns and Dorset in 2002 and 2005 will be reassessed and in light of the recent research they may well be found acceptable.

Royal Tern Thalasseus maximus

DNA analysis has shown that although the 'Royal Tern' of North America and the 'Royal Tern' of West Africa look pretty much identical, they are in fact distinct species, with the West African bird being more closely related to Lesser-crested Tern than to the North American bird.

Red-winged Blackbird Agelaius phoeniceus

One on North Ronaldsay, found on 29th April 2017 and present till at least 7th May 2017

"Masked Wagtail" Motacilla alba personata

This race of White Wagtail was found in Pembrokeshire in November 2016 and will presumably be admitted to category A following review.

Western Swamphen Porphyrio porphyrio

One in Suffolk and Lincs from from July to November 2016

Lammergeier Gypaetus barbatus

One at various sites in Gwent, Devon and Cornwall in May 2016.

Dalmatian Pelican Pelecanus crispus

One at various sites in Cornwall and Devon between May and November 2016.

Seaside Sparrow Ammodramus maritimus

One was on board a ship that departed N America in May 2016 and was still on board when it docked at Southampton and North Shields later that month.

"Eastern" Common Tern Sterna hirundo longipennis

A Tern in north Norfolk during August/September with an all-dark bill was considered to be of the race longipennis but no determination has yet been made. Another was in Northumberland in April 2015 and yet another in Northants in May 2017.