Slaty-backed Gull: variation in saddle shade

How many shades of Grey? Slaty-backs and Vegas milling around an outfall on a calm sea. This is not unlike one of those kids puzzles where you have to find the matching pair amongst all the similar looking alternatives. Only in this case there isn't a matching pair to be found.

I took the above shot in Mie early in March 2016, it was one of the rare days at the site that the sun and wind weren't trying to out-do each as the biggest obstacle to gulling. At the time I was intent on the two Slaty-backs (second and third from the right) and their differing saddle shade. It was only back home going through the images that I noticed the Vegas are doing their level best to express their individuality in this shot too.


On more than one occasion concerns have been voiced about the paleness of some potential Slaty-backed Gulls in Europe and North America. I've struggled to see the problem in images of the birds I've seen, more often than not I see perfectly normal saddle shade for Slaty-back from my Kansai perspective.


To me surprise goes in the opposite direction and every so often I come across a really dark Slaty-backed that stands out from the crowd and I wonder if this is what observers elsewhere expect to see from a vagrant. The vast majority of birds I see aren't so much darker than the dark end of the Vega spectrum. It's very doubtful you'd notice a 'local' Slaty-backed if quickly scanning a Vega flock, especially in sunny conditions. Perhaps observers coming to the region in winter and seeing Slaty-backed against a snowy background might get the impression of a much darker gull? Personally I never see the SBG/snow combination... fortunately. Coming back to the above image, if we could switch on the sun, at a glance the paler of the two SBGs probably wouldn't appear any darker than the Vega on the left as they turn and twist on the water.


Olsen's Gulls says there's "very little" geographical variation and cites King & Carey (1999) that northern populations tend to be larger and possibly have darker upperparts. If it's true that there's little Geographical variation, then the difference I see here must be down to individual variation and in that case I'd conclude that very dark birds are scarce to rare. I wonder whether observers further north would disagree?

This is the darker of the two Slaty-backs in the opening image and it's the only strikingly dark SBG I have images of from recent years apart from the gull last weekend. Older digiscoped images are of much lower quality.

This is a slightly lightened image of the same bird. In all these images, at differing angles, the most striking feature to me is how little contrast exists between the saddle and primaries.

The following images are all from last weekend and include my first 'super-dark' SBG of the winter. It's always worth bearing in mind Vega shows a wide range of saddle shade.

This is the local SBG gold standard, and the very distinct contrast between saddle and primaries is obvious. Images of gulls always don't always convey the reality of the observers' experience, it's often so difficult to judge shades of grey from images; different angles, different light conditions, birds compared with different individuals and so on. However this saddle/primary contrast is unequivocal and I think the clearest way to indicate the difference between the lighter- and darker-saddled birds. 

And another typical SBG.

The same SBG with a Vega. This SBG my be standard in appearance but it didn't seem the brightest SBG on the beach, it repeatedly brought its catch back to the same spot where the same Vega would steal it.

The same bird on its (rather pointless) hunt for shellfish.

Another SBG in flight, here looking slightly darker only as a result of the angle.

I was quite happily getting shots of typical Slaty-backs when way along the beach I spotted a 'black-backed' gull. This had to be a dark-end SBG; the other candidates would all be first records for Japan. So off I went, as fast as the softer sand higher up the beach would allow. The light was a tad bright by the time I got there and, if anything, even better to bring out the shades of grey.

Dark-saddled Slaty-backed Gull with Vegas (2 Feb 2018). These gulls are clearly blackish-backed whereas the standard birds are... well, slaty.

Again, from a different angle there's still little contrast between saddle and primaries.

A standard SBG (sub-adult) with the dark adult to the right. That's a Taimyr Gull in the background.

The typical sub-ad SBG on the left and a Vega on the right. This was as near perfect gulling light as you could wish for.

A more heavily cropped version with just the two Slaty-backs.

A few interesting recent gulls

This is just a quick post to show some of the gulls I thought interesting (for one reason or another) recently. I have mountains of gull images that never see the the light of day, in fact there are files full of images I haven't got round to checking at since the day I took them! Most of these gulls I saw during my last two visits (January) to Mie.

A presumed female Taimyr judging by size. This gull really caught the eye because not many have such yellow legs at this time of year. The moult is at the faster end of the progress scale but not unusual, a couple of other birds had p8 as the longest new feather. Towards the other end of the scale I noticed one gull that hadn't dropped its old p8 yet. 

P8 effectively black to the coverts, it's just becoming blackish-grey proximally though this probably wouldn't be obvious at a any distance. P7 is also extensively black and the black notch on p4 is also fairly standard.

A remarkably small p10 apical spot which at this moment is twinning a tiny p9 mirror.

It's a smallish gull, here with Vegas, I think it's going to have very long primary projection in relation to the rather short tail length when the primaries are fully grown.

With a first-winter Taimyr in the background. Thoughts of possible barabensis crossed my mind at the time but being realistic the fresh primaries due to much later and ongoing moult plus the lack of expected bill markings rule that out. 

The same first-winter Taimyr. The narrow pale tips have worn of the tertails, and fringes from the inner greater coverts, creating a very uniform appearance.

Another adult Taimyr, this still with three retained outer primaries. In the field the legs were pinkish overall as they seem in this image but less so than Vega, on closer inspection however the back of the knee was distinctly yellow and the rear of the tibia only slightly less so. This is closer to the norm at this time of year rather than the bright yellow of the earlier bird.

Mongolian Gull? Here as part of the flock and a couple of heavily cropped individual shots below.

A white head in the flock is always worth checking but a number of Vega can stay surprisingly white-headed through winter. However this bird's structure and extensive black towards the bases of the primaries all looked good for Mongolian (I didn't get flight views) so I was really taken aback to see it hadn't completed its primary moult. All but the very earliest arrivals in November seem to have already completed their moult, perhaps not unexpected in a southern breeder. This bird was even behind the vast majority of Vega in its timing. I still think it is a Mongolian, but one with a noteworthy late moult. 

Vega with a white band through the sub-terminal black of the tail are very scarce rather than rare but this bird wins first prize for style; I've never seen such a well banded tail on any other gull. As for it being a pure Vega... well, it's at the whiter end of the spectrum but nothing to write home about, the oddest features (other than the tail) are its very short legs and small size.



If I had that tail pattern, I'd want to keep it into maturity!

There's nothing in the plumage to indicate it's a hybrid as far as I can see, it's simply a very distinctively patterned bird.

For me this is a particularly dark Slaty-backed, I see a small number like this but they aren't the norm in this region at least.

The same bird in the foreground later in the day. The other Slaty-backed has a more typical saddle colour, in this region certainly. 

This was another dark bird last winter, in flight there was almost no contrast between the outer primaries and the rest of the wing. 

First-winter Slaty-backs show enormous variation but this gull looks good for Glaucous-winged, a bird I rarely see in Kansai.

First trip to Mie 2017

I haven't had so much time to get out birding since the Kyushu trip but I managed a short visit to Mie last week, just before winter finally arrived.


Early in the day, in fact for most of it, the wind was strong which made checking the sea difficult and the stubble and overgrown fields next to impossible. Coupled with very bright sun and not quite catching the tides as I'd like birding was anticlimactic by the area's very high standards. It wasn't until late afternoon that the wind dropped and some clouds gathered making looking at the gull flocks worth a punt. The most notable thing being not a single Taimyr Gull was to be found.


The day will stick in the memory for two things though. Firstly I finally got good flight views of our local Turkey Vulture and secondly the very un-Japanese scene of a dead bull lying in a dusty unmetalled company parking area! This was so jarring that I had to stop and take a photo.

Not something you see everyday in Japan, not something I've ever seen in Japan actually. It doesn't look freshly dead either and the crows seem to have been at the eyes.

With wintering Steller's Sea Eagle in the region we're no strangers to the spectacular but this bird definitely adds to the Mie experience.

On the wader front, I saw a single Ruddy Turnstone, a couple of Eurasian Curlews and a handful of Common Greenshank, as well as the more numerous Kentish Plover, Sanderling and Dunlin. On the landward side of the seawall were Common (3), Wood (2) and Green (4) sandpipers. With so many waterlogged fields it isn't surprising there weren't any concentrations of Common Snipe and I only saw four.

Wood Sandpiper

Green Sandpiper

Common Snipe

Early in the morning a white-winged gull flew over the car and directly away from me along the seawall. Whether this was an immature Glaucous or a leucistic Vega I wasn't able to tell, though I later learnt a first winter has turned up in the area. Later in the day the adult Glaucous that's taken up seasonal residence here was out on a distant sandbar off one of the estuaries. As well as the absence of Taimyr Gulls I already mentioned there were no Black-tailed either, perhaps they have already returned to their breeding colonies, certainly numbers dwindle to almost zero at this time after having been common till about the turn of the year. On the other hand Common Gull numbers have begun to increase, I don't know why they are relatively scarce in early winter as there are always good numbers through the latter part of the year in Osaka, just across the peninsula.


The small flocks of gulls scattered along the beach north of Tsu were Vega almost to a bird, there was one probable Mongolian which disappeared before I could get confirmation and what appeared to be a Vega x Slaty-backed hybrid. Adult gulls that show obvious signs of hybrid origin, particularly the Vega x Slaty-backed combination, aren't common. Hybridization seems far less frequent on this side of the Pacific, or at least so I gather, I don't have first-hand experience.

The dark-saddled gull stood out among the Vegas on the beach but only because of the shade, structurally it was a good fit with the others so I wanted a better view.

Coming at it from the other side it was no less eye-catching. In fact I might have taken it for a Slaty-backed on this view alone.

Dark-eyed Slaty-backs do occur but they're very thin on the ground, this bird has heavily peppered irids. The primary projection gives the impression of being on the long and narrow side for a Slaty-backed too. While the saddle is too dark for Vega, a typical Slaty-backed would look a little darker in this light. 



This typical Slaty-backed just off the beach didn't come ashore with the other gulls so there was no chance of direct comparison.

Hooded Cranes in Mie

There have been a few Hooded Cranes in Mie the past couple of weeks, they do turn up occasionally in Kansai at this time of year. One even over-wintered at Lake Biwa a few years ago. I'd hoped to run into them on this visit (November 20) but I hadn't the previous time so wasn't optimistic. There was no sign of them on the fields I normally cover, there are plenty I don't, so I'd all but written off any chance of connecting when I came across this bird way out in the middle of a river mouth. I presume it had gone there to bathe but it was a really odd sight, a crane belly deep in a wide estuary.

After a while it took flight and came down on a scrap of arable land tucked away in a group of houses.

Things are getting slow on the wader front, Greenshank do winter here so seeing them wasn't a surprise. There were no Grey-tailed Tattlers and just a single Terek Sandpiper even though both had been very common a short time ago. Red-necked Stints have disappeared too but winter waders such as Dunlin, Sanderling and Oystercatcher are building in numbers.

Common Greenshank.

Terek Sandpiper.

Little Grebe is common but rarely close enough to photograph.

There were big numbers of gulls on distant sandbars off-shore but unfortunately only a few more accessible birds loafing on the beach north of Tsu. Vega numbers are building rapidly now but there were only three Taimyr still present.

A very typical Vega at this time; p8 is in and only a handful have retained outer primaries. The bird below is the exception that proves the rule I suppose. This was a real surprise a Vega outer primaries but only new p6 in place. 

Juvenile Vega.

Juvenile Slaty-backed.

The following bird is another juvenile Slaty-backed though I thought it was going to be a Taimyr when I first saw it and it's a great example of how variable they can be. The smaller size, initially less Slaty-backed head shape and much blacker looking primaries had me fooled at first. Looking more closely the Slaty-backed head shape became more apparent, the primaries may have been blacker than expected but the blade was very broad and the underside distinctly pale. Slaty-backed it is then...

The very black primary projection is odd for Slaty-backed but it's very deep and the pale underside of the far wing are the first give-aways that this is a Slaty-backed. 

The head shape is getting more like a Slaty-backed here. That's a more typical Slaty-backed behind it. 

Suddenly it couldn't possibly be anything else!

Other birds of interest were the first Goldeneye and Red-breasted Mergansers of winter but Common Shelduck doesn't seem to have arrived yet. The first Black Brant has also turned up though I didn't see it. There were several Dusky Thrush even though there were only a couple further north in the mountains earlier in the week and the following day there were even quite a few at work just south of Kyoto city.