www.gull-research.org

To get a better idea of the possible extent and variation, it may be interesting to ad links here and a picture.

1st example, a very advanced bird at Hannu's site:

"the weirdo" - http://www.elisanet.fi/hj.koskinen/2cya ... 80412.html

Lousy long distance (200 m) shots but note replaced tertials and coverts on both sides. A YLG would be proud. Heemskerk, 11-04-11.

I would vote for a ylg on this one, Ruud.
given the tertials, patterns onthe frsh coverts..

Theo

Theo I think you're right!