What is the taxonomic status of this form of Lesser Black-backed Gull please?
Presumably you mean Yellow-legged Gull?
This form is not considered to represent a valid subspecies, and has been absorbed into larus michahellis michahellis (leaving larus michahellis atlantis on the Azores, as the only other recognised race of Y-l Gull).
This treatment is used by the current versions of both the IOC World Bird List (version 3.0b) and Clements Checklist(verson 6.6), and also Olsen and Larsson in their book "Gulls of Europe, Asia and North Africa".
lustanius Yellow-legged Gulls are described by Olsen and Larsson, and apparently have some DNA sequences that are intermediate between michahellis and atlantis, and differ slightly from michahellis in some respects, but they give the name L. m. 'lustanius' only in 'quotes'.
Thanks. Most helpful.
I should probably have said that the taxonomy of the 'large, white-headed gull species' is currently in a state of flux, with different authors and taxonomical bodies often recognising different species/races as valid.
It may be that in the future lusitanius does gain universal recognition as a valid subspecies.