www.gull-research.org

Hello all,

This weekend, Rob Hoeben and I were checking our local gull spots in Leiden (The Netherlands) and came across two gulls with extensive scapular moult. This led us to believe that these were Yellow-legged Gulls, but we can't exclude Lesser-black Backed Gull when taking other characteristics into account. Since our experience in both species at this age is somewhat lacking, we seek your advice...

Individual #1:








More pictures on Rob's site:
http://www.pbase.com/hoeben/inbox

As you can see, there is extensive moult in the scapulars, letting us believe this to be a Yellow-legged. However, we would expect the tail pattern and inner primaries to be lighter in case of a YLG, and would fit a LBB better. Or do both characteristics fall within the range of variation for a YLG?
Also, we found an example of a YLG on Ruud's site which closely resembles the Leiden individual (although younger and therefore slightly less advanced in moult, and the tail pattern seems lighter): http://www.xs4all.nl/~daarruud/michahellis1l.html.

Individual #2:



Again, extensive moult in the scapulars. Enough for a YLG? We weren't able to find any examples of LBB's with such advanced moult at this age…

Any comments are much appreciated!

Regards,

Maarten & Rob

Both birds are Lesser Black-backed Gulls.
Advanced moult in the scapulars has been documented by Theo, Mars and others at De Maasvlakte and Dintelhaven.
See http://www.gull-research.org/lbbg1cy/lbbg1cyjuly.html for more information.

The inner primary and tail pattern together with the overall freshnes further suggest LBBG

Jan

Many thanks Jan, that confirms my suspicion.