surfbirds.com - Lesser Black-backed Gull Ageing Discussion

The ageing of 2nd-and 3rd-calendar graellsii is very difficult, due to the large variation in its appearance. The timing by which it acquires adult plumage is said to be akin to Yellow-legged Gull L. michahellis, and a lot of what is written here can be related to it. In practise, Herring Gull L. argentatus is all over the place.

During its second-calendar year, a graellsii moults from first-winter to first-summer plumage, by a moult if its contour plumage (head and body feathers), then to second-winter plumage, via a complete moult.

(All images taken at Blythburgh, Suffolk in June or July 2000 by Brian J. Small)

If you look at the "first-summer" graellsii images, you will note that in general they seem to fall into two categories: firstly, those which look more immature, lacking plain dark grey plumage (see Fig.1. below "1st summer" graellsii"- left hand bird)

Fig.1. "1st summer" (left) and "2nd summer" graellsii

secondly, those with a mixture of old worn and new, plain dark grey feathers on the mantle and median coverts (see Fig.2. below "1st summer" graellsii)

Fig.2. "1st summer" graellsii

Some of those aged as first-summer may well be those graellsii with a more retarded plumage in their second-calendar year looking more immature in the third – and may account for the variability of the bare part colouration (see Fig. 3. below "1st summer" graellsii - where in comparison to the others, the bill is more adult-like).

Fig.3. "1st summer" graellsii

A lot of questions arise. For example, is Fig.4. (below) "1st summer" graellsii actually a first-summer? It is rather white headed in comparison with the others and the coverts are incredibly bleached. Has it simply spent more time in its winter quarters? The mantle looks similar to Fig.2. (above), but that bird has advanced moult of the median coverts and might be a second-summer.

Fig.4. "1st summer graellsii"

This discussion is continued on the next page...