© A. R. Dean

Second and third calendar year Lesser Black-backed Gulls can be difficult to age, as there is variation and overlap in their appearance and the timing of moult. Some first summer birds, for example, are more advanced than others. Typical first-summer birds are distinctly untidy and show very few if any new, clean, grey feathers in the upperparts. Others, however, show quite extensive new grey feathering in the mantle and wing-coverts, and such birds can be difficult to distinguish from older, 3cy (2S) individuals. Similarly, it is likely that some 3cy birds do not appear as 'advanced' as others, and resemble the more advanced type of 2cy individuals. In the photo above,  the left hand bird is a fairly typical 2cy graellsii. Even here, however, note the difference in whiteness of head and underparts and in bill-colour compared with the right-hand bird. The right-hand bird shows more advanced mantle and coverts, with quite extensive new plain grey feathering, as it moults into second-winter plumage. Note, conversely, that the bill colour of this individual is darker and less advanced than the bird to its left. Such extensively dark upperparts are not typical so early in the second calendar year (except in nominate fuscus) and older individuals (in second-winter) can look much less 'advanced' than this. Thus, ageing of some 2cy and 3cy Lesser Black-backs is somewhat speculative.