What do YOU think?
It’s part of the challenge. I regularly tell folks the more Gull species you can identify in a flock, the more often you’ll find tricky ones too. Skills definitely go up but so do the challenges. This was a fascinating bird.
Had a strong juvenile Caspian Gull feel on first view. Head and bill shape especially and the retained juvenile scapulars only have a narrow fringe. I did flirt with juvenile fuscus briefly. It was easily the most aggressive gull in its area. Thus head and bill structure etc and striking tail pattern (Caspian-like), juvenile scapulars, longish wings and behaviour all suggested Caspian. However in flight it has big primary window, rather smokey-brown looking underwing covets, though underside of primaries looks quite whitish in the video. Greater coverts and tertials more Herring Gull like overall. Working hypothesis as argentatus x cachinnans? Back there on Saturday, hope it’s still there.