The same day I saw the recent
adult Thayer's I also came across this second-winter gull. I hadn't seen much of interest up to that point and this gull was the judges overwhelming choice for bird-of-the-day if it hadn't been for the Thayer's appearing at the death and pipping it to the accolade.
I haven't seen a hybrid quite like this before and I'm curious about its parentage, for each potential combination there is something that doesn't quite sit comfortably. The only thing I would put money on, is that Glaucous-winged is involved. Money, but not the house. And if my arm were twisted, I'd plump for Vega as the other progenitor.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfmb0BVGDpifVqRMTFM_bd46x25nv26WVN2ITsps1KRn00do8pgD-qkBMOUA2ipW9Zk3A5CK8w1AiTWsbbqOljMpaqxa3T45U0khgNZ5tb9eNjV6Os_OCbyn_3kTOP3nI0Z17qz2pb0np-/s640/Y98A0250.jpg) |
So here's the bird. The smallish size, to an extent structure and aspects of the plumage could be highly suggestive of second-winter Thayer's. The head looks fairly rounded in this image and notice the white far-wing. |
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWcZv4s2S88Z82tnS2YyHNLVy1orWPnfyByBf-r-Z-ehvQRIx6p4v3ebHJdB4qpMlqSSGnjEaN7ITBIRzPy7SPxNZIbW-MMTdWjQc2YIJa3KoCnQlHYxxdeiSP-guKRE2wRRAXeYmmCqFd/s640/Y98A0114.jpg) |
Another angle and the head looks much heavier, as is the bill towards the tip, more of a Glaucous-winged feel than Slaty-backed. The body was only about the size of a smallish Vega. |
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhq6qMo-u_EFbL1whp1s7A5aW2KwQyEIprekStx6mIB3Mw5ZcK5zotjHnqLQUxCL7qONb3WxjI0b6ySz6zFrE0HrNDHc9cYgZFsrRS64BEfRBHsOjl0YYM5pZz5vE9nL-dJvkVrgxe75bIo/s640/Y98A0178.jpg) |
Glaucous-winged x Slaty-backed is a logical choice in Japan but they both are relatively short-winged, typically with a deep-based and blunt-tipped primary projection but this bird is distinctly long-winged and that combination is highly unlikely to produce it. There isn't much overlap in breeding ranges of Glaucous-winged and Vega which may explain why I've never (knowingly) seen that hybrid. Vega x Slaty-backed, which I have seen, is more likely because of a greater area of sympatry according to range maps but I don't think there's much to suggest Slaty-backed about this gull. |
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiYCJNQPKxcKrxo06e6GFwbLbFJUDT1KcTA4SvzcFkAU4m4cdyNw3_tXfB7l7x4th7Krrvmf_7Hz4KoWxKZ3f_NW_ea044rITwDLwawE46a6OXOuMTcSwxXgo0VVq5iNhltt2n7qTHqUVAw/s640/Y98A0245.jpg) |
In this view the stronger light means the upperside of the primaries looks much greyer compared to the previous images, while shadow creates the darker underside. |
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-sO3uBeoH3YLH8smNbAhGFkGB_Dbr15nc2gslfZTAec2ohjJvt1C9D8CyYxjoQFKkm23QTHeJJdhQPIr1zTa58UaQgimVo3ifhR6aBGilME6lhvvX8087e3re6gZ3GUyT_NDwlQ6PHFQj/s640/Y98A0147.jpg) |
The tail is still quite solidly dark and there's a ghost of a p10 mirror. |
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTOANx85QG5HUzQIV8tpcOtzqYkPktqMzZ-ndRtM8m0lUXMNZOKj0sGp6LEdjRGhtQfoL8neeWgmVwf5kMuCjjzDPR3wmlk50L70HcLs4oDssndHl1nfljfoFUagiMvYX8He8RXuyDEqzC/s640/Y98A0154.jpg) |
The upperside of the primaries has a Glaucous-winged feel with a clear difference between inner and outer webs. |
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDQ-z-DaAdFYH72H6tBM8vFTSSXf_jNhpFlHyA-tyZ_5MCRSixPxk8FlzjPRXMY2hvlFR8ycbAUq92OaCtu7Tn_fOlk9qCjJ6mhqOTNOa2dkOnQT33-A1Wh56lzeL9dvyMEOrXdQ0oRRtd/s640/Y98A0253.jpg) |
If it is a Glaucous-winged hybrid it might even be worth considering a New World combination, there seem to be plenty of hybrids across the water and Glaucous-winged x American Herring Gull ranges have significant overlap. This could account for the longer-winged appearance but surely such a hybrid would have a paler saddle and so seems a non-starter. The larger mirror of the underside of p10 is just visible on the upperside. |
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