I don't think the ABA is at all comparable to the UK400. For one, they strictly follow AOU on taxonomy, common names, etc. They also have an actual committee to vet sightings. UK400 is basically up to the whims of one person, with changes motivated as much by year lists as any change in science.
Also U of Alaska has been collecting on the islands for a long, long time. I doubt ABA had any role in their decision to collect those birds.
World: 1194, ABA: 626
Last Lifer: Sedge Wren
Last ABA:Sedge Wren
Mammal: 230 Herp: 174