Tuesday, 21 February 2017

A hybrid gull... but what parentage?

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.

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.

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.

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.

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.

The tail is still quite solidly dark and there's a ghost of a p10 mirror.

The upperside of the primaries has a Glaucous-winged feel with a clear difference between inner and outer webs.

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.

Tuesday, 14 February 2017

A few other birds on the beach

It can be tough getting a good shot of Greater Scaup, they're often closest when in harbours rather than the open sea. On this occasion, standing on the tideline checking gulls, the birds were cruising the tideline and coming to me.

Immature Red-breasted Merganser

It wasn't just ducks off the beach, there were waders on the beach, mainly Dunlin, Sanderling and these Kentish Plovers.

Kentish Plover

And of course more gulls. There are plenty of atypical Vega around vying for attention, this was a nice one...

Distinctly small with shortish, purple legs. The saddle really is darker than the other Vega even though the different angle doesn't normally allow a meaningful comparison.

Extensive white in the outer primaries isn't unusual, a significant minority show this.

The fine streaking on the very rounded head and the bill slight are sufficiently unusual to catch the eye. However all the features shown by this gull can be found sifting through a flock of Vega, it's the combination of delicate head along with that saddle shade, the legs and wing-tip markings making it worth the attention.  

Saturday, 11 February 2017

Thayer's Gull on the beach

I'd been keen on getting across to Mie all week to sift through the gulls but by Friday night snow had been falling heavily (by local standards), more was forecast for Saturday, and a night drive over the quite mountain road wasn't so appealing. But never underestimate the pulling power of gulls.

I left at 01:30 and with half the distance covered I was almost the only vehicle on the road crunching and bumping over ridges of frozen car-tracked snow left by those who'd already reached their destinations at a sensible hour. It was the dark areas with now snow that were the most worrying though. With the climb towards the pass now before me I stopped off at a convenience store and wasn't so surprised to find a few late night travellers making the best of a bad job. Fortunately I was now within easy striking distance of the ever-busy Meihan National Highway, it meant a roundabout route to the coast but it would get me round, through and under the mountains. About 60 kilometres to the north of my destination seemed preferable to inching directly over the top.

I arrived at dawn, later than hoped for, only to find the wind blowing a gale under a clear sky. Not exactly gulling conditions (the forecast had said overcast all day with frequent snow flurries... but what do they know!). In the event I put off going to the gull beach till mid-afternoon by which time it was plain there's be no improvement in the weather.

There were far more gulls than I've seen so far this winter but the vast majority were hunkered down in tight groups facing into the wind and without my scope, purposely left in the car, there wasn't much to catch the eye. just before the light started to fail and I found this adult Thayer's. I'd seen my first ever adult Thayer's less than a year ago on this same beach but then I'd known there was one in the area. This bird was far more satisfying, both a total surprise and giving better views.

As you can see from the following series of images the light quickly faded and though the Thayer's didn't fly far there wasn't any point in following.