EURO Herring. Carlyle

[troglodytes]

Euro Herring also often show white in the outer tail.  Truth to tell the more we find out the less we know.  Once a species like LBBG gets a toe hold in a new place,  in the absence of its own species the next nearest will do and so F1 hybrids.  Next problem - back crosses in the F2 with F1 or parent stock.  Interesting isn't it.

BTW Herring /  LBBG used to be what was called a ring species ie they changed gradually across the globe, but were essentially a single super-species.   Sorting out the parentage of gulls is at the very forefront of avian identification