|possible Caspian x Herring Gull hybrid, Selsey, 12/11/2017|
The paleness of the bird led my mind to Caspian from the off, but a few things left me confident it wasn't one, namely the head/bill structure, the posture of the bird and lack of grey in the mantle and scapulars.
|note the pale underwing and tail pattern|
For some time I explored the idea of it being a Yellow-legged Gull, but again, something didn't fit. The scapulars looked promising for this, but again the head structure (and lack of mask) threw more confusion on from the outlet, as well as the general shape of the bird. Ultimately I veered away from Yellow-legged - a lack of wear in the tertials, and moult in the coverts reaffirmed this.
The poor case for Yellow-legged seemed to be emphasised when the gull took off, and the tail band particularly suggested something more Caspian than Yellow-legged. Furthermore, the bird showed very pale underwings, a large inner primary window and even, at times, a seemingly grey-ish mantle!
|the pale underwing shows obviously here|
I was truly stumped, and it was time to contact some gull gurus. By this point I'd tried to make the bird a very pale Herring, and suggested as much, but opinions varied, most favouring Caspian. However, ultimately the opinion offered by Josh J is what I feel is most likely, and indeed an option I hadn't thought of - a Herring, crossed with some Caspian genes.
This bird was just not full Casp, but had enough features to suggest there was some cachinnans genes in there for sure. It could even be an extreme variant of argentatus Herring, but I personally feel it's a bit of a cross. Whatever the case, a very educational session indeed. Thanks to all who offered opinions, and I'd be extremely grateful to hear from anyone who can offer any more thoughts!
|almost grey appearing mantle, and wide primary window|
|pale head and breast, and dark tertials with thin white|
Most of the large gulls were Herring, though there were a few 1st-winter Lesser Black-backs, as well as a sole 2nd-winter Great Black-backed. A good amount of Black-headed Gulls were also around, as well as a sole, foot-less Mediterranean Gull, that seemed to be suffering no side effects as a result of its unfortunate situation.
Other birds of note included an extremely confiding flock of Turnstones, several Cormorants offshore, and a single Sanderling.
|and a legless Med Gull to finish|