First-year Yellow-legged Gull (Larus michehellis) Versus First-year Lesser Black-backed Gull (Larus fuscus)

Yellow-legged Gulls turn up in Southern England on a regular basis and are readily identified in all their guises by experienced gull watchers. I have made it my mission to learn the complexities of this species and trips to the Algarve last year and again recently have really helped. Possibly the most difficult age for birders to identify is juvenile and first-winter. With this in mind, I attempted to take lots of images of first-year birds during my trips.

The text book features of a first-winter Yellow-legged Gull are: large and brutish looking, a whitish head with a dark eye mask, greyish mantle and scapulars feathers with dark anchor markings, contrasting brown wing coverts and dark brown pale-edged tertials. The bill is usually black or mostly black and the shape is distinctive, being relatively short and appearing heavier towards the tip due to the steep gonys angle. Lesser Black-backed Gulls are often found with Yellow-legged Gulls and this is the species that is most likely to cause confusion at this age. 

The first four gulls below are classic first-winter Yellow-legged Gulls and identification should prove fairly straightforward:

First-winter Yellow-legged Gull

First-winter Yellow-legged Gull - Late September 2014

First-winter Yellow-legged Gull - Early October 2014

First-winter Yellow-legged Gull - late September 2014

The next batch of images show first-winter Yellow-legged Gulls with slightly darker heads. The advanced state of moult helps to identify them as Yellow-legged Gulls, but by the end of September some Lesser Black-backed Gulls, in their first-year, will have second generation scapulars. Care must be taken to avoid making assumptions based on moult during late autumn. Size and structure helps, as does the distinct shape of the bill. 

First-winter Yellow-legged Gull - Early October 2014

 First-winter Yellow-legged Gull - Late September 2014

First-winter Yellow-legged Gull - Late September 2014

First-winter Yellow-legged Gull - Early October 2014

First-winter Yellow-legged Gull - Late September 2014

First-winter Yellow-legged Gull - Late September 2013

First-winter Yellow-legged Gull

First-winter Yellow-legged Gull - Early October 2014

The individual above is small, so presumably a female. The bill shape is typical for Yellow-legged Gull, as are the dark pale edged tertials and the dark anchor markings on the scapulars. It is quite long winged, but I feel it is most likely to be a Yellow-legged Gull.

First-winter Yellow-legged Gull - same as above

During early October I saw a few first year Yellow-legged Gulls that were still in juvenile plumage. By late August first-year Yellow-legged Gulls are usually further advanced in their moult into first-winter plumage. However, not all of them are born earlier than Herring and Lesser Black-backed Gulls. I watched two juvenile Yellow-legged Gulls food begging from an adult at the Portimao Fishing Harbour on October 4th this year. It is, however, usual for Yellow-legged Gulls to be born earlier than the other two species.

Juvenile Yellow-legged Gull - Early October 2013

Juvenile Yellow-legged Gull - Late September 2014

First-year Lesser Black-backed Gulls are similar to Yellow-legged Gulls when both are in juvenile plumage and again when Lesser Black-backed Gulls start moulting into first-winter plumage. That said, most first-year Lesser Black-backed Gulls are easily identifiable based on structure when compared to first-year Yellow-legged Gulls. The selection of juvenile/first-winter Lesser Black-backed Gull photos provide interesting comparisons with the Yellow-legged Gulls images above.

First-year Lesser Black-backed Gull - Late September 2014

First-year Lesser Black-backed Gull - Late September 2014

First-year Lesser Black-backed Gull - Late September 2014

The juvenile/first-winter Lesser Black-backed Gulls above are all fresh looking, small and not at all brutish looking. The one below does look a bit more brutish looking but is still a Lesser Black-backed Gull.

First-year Lesser black-backed Gull - Late September 2014

The gulls below proved difficult to identify. 

The first one is quite advanced in its moult having replaced most of its mantle and scapular feathers. It has a pale head, which points towards Yellow-legged Gull, but its wings are long and its size and shape is more Lesser Black-backed Gull like. My gut feeling is that it is a Lesser Black-backed Gull, but I'd be interested to hear any other opinions.

Probable Yellow-legged Gull - Late September 2014

The next one has replaced many of its scapular and mantle feathers, but it is not an obvious Yellow-legged Gull. However, its black bulbous tipped beak suggests Yellow-legged Gull, as does it large head.   

Probable First-year Yellow-legged Gull

The one below is quite a difficult one. It is large and robust, but also quite slender. Its moult is not as advanced as most first-year Yellow-legged Gulls and its bill shape is quite long and slender. Weighing up the odds I feel this one is most likely to be a Lesser Black-backed Gull - probably a male.

Probable First-year Lesser Black-backed Gull - Late September 2014

The next one below is a Yellow-legged Gull, but its coverts are non-typical. They are very chequered and paler than normal. This one could prove to be challenging if seen in Britain.

First-winter Yellow-legged Gull

Another Yellow-legged Gull, but this one is slender and small headed. Its bill is quite parallel sided but not that long. This one could again cause some difficulties if seen in Britain.

First-winter Yellow-legged Gull

The last one is hardly brutish, but it is most likely to be a small Yellow-legged Gull based on the bill shape and the moult status. It could be a Lesser Black-backed Gull, but if so it was much further advanced in its moult than all the other Lesser Black-backs. 

Probable Yellow-legged Gull

Some Yellow-legged Gulls are much smaller than the typical ones like the adult below:

I hope you find this informative and not too heavy going.