Green XNCJ on Lake Constance - Caspian or hybrid?

[Jeremy Barker]

This morning at the Rotachmündung, Friedrichshafen were the ususal mixed bacg of cachinnans, michahellis and things which look - to me - to be somewhere in between. One of those is an adult-cycle (?) bird with green ring XNCJ, which should come from the Lausitz area on the Polish border. I hope. In comparison with the standard cachinnans around it, it looks a little different: shorter-legged, shorter- and deeper-billed, brighter bare parts (roughly what I associate with 3rd/4th cycle michahellis) and a more compact body and rather more head-streaking than any of the other adult-types present today. If anyone with more practice at the variation within cachinnans has a view on whether this is within the range of normal or not, I'd be interested...

All the pictures are crops: sorry if the quality isn't good enough to judge the bird's identity!