Friday, 23 February 2018

Choshi (6): Common Gulls

The last remaining gull species of interest to me present at Choshi in reasonable numbers was Common Gull Larus canus. Despite a lot of individual variation, I assume all of those I saw there to have been 'Kamchatka' Gulls L.c. kamtschatschensis. As a first-winter, this form retains more juvenile plumage until much later in the winter than other forms of Common Gull, and it wasn't that difficult to find one or two that had replaced practically nothing in their saddles.

Most had replaced at least some feathers, though, but I didn't come across any that had replaced all (as I remember being the case with L.c. canus in the UK). The most obvious variation at this age was on the underwing, with some having very dark underwings with largely solidly brown axillaries, and others having a much whiter underwings with brown-fringed axillaries. I have it in mind for some reason that white-looking underwings are a characteristic of L.c. heinei, but that these need also be accompanied by an entirely white body (without dark blotches or streaks).

Remarkably, I returned from Choshi with only one second-winter Common Gull on my camera. This, too, was a rather dirty-looking thing with its solid brown collar/shawl.

The adults were overall less remarkable than the immatures, though there was plenty of variation in wingtip pattern amongst them in just the handful I shot. The first bird below shows limited black in its wingtip, with black reaching the primary coverts only on P10 and a largely grey P8. The second bird (third photo) shows more black at the wingtip, with black on P10-8 reaching the primary coverts and a largely black P8. The third bird (fourth photo) had plenty of black at the wingtip, but also three mirrors. The last (and largest) bird has quite a long (but diffuse) tongue down P8!

So a medium-sized gull of interest to complement all the large ones. All in all, despite the best part of four days there, I still feel I only scratched the surface at Choshi and a return visit in an upcoming winter would be highly desirable! Above photos taken at Choshi Harbour, Chiba Prefecture 6-9/2/18.

Tuesday, 20 February 2018

Choshi (5): Vega Gulls

Like adult Slaty-backed Gulls Larus schistisagus, adult Vega Gulls Larus vegae pose few problems at Choshi. Also, like Slaty-backed Gulls, they are everywhere and permit as good a 'grilling' as any bird you're ever likely to encounter. Not surprisingly, they showed variation in some features (e.g. wingtip pattern, shape and length of P10 tongue). However (though I made no attempt to undertake a 'comprehensive survey'), in others they were remarkably consistent (e.g. leg colour, invariably pink, with the pink varying only in its intensity). Below is a sample of typical adults.

I was also delighted to find that the colour of the orbital skin seemed quite consistent in Vega Gull (in photos at least), or at least did so in those close birds I photographed well. This was a difference from Taimyr Gull Larus taimyrensis I had noticed in birds I had been identifying as Vega Gull earlier in the winter back in Taiwan. Adult Vega Gull has rather bright orange-amber orbital skin, unlike the vinous-pinkish-red of Taimyr Gull (and the pale flesh-pink of Slaty-backed Gull). Below is a composite (with all photos taken in Choshi) showing the orbital skin of two Vega Gulls (top), a presumed Taimyr Gull (bottom left), and a Slaty-backed Gull (bottom right).

As with Slaty-backed Gulls, I spent an insufficient amount of time looking for and at 'interim' plumage stages of Vega Gull as (once the first few adult-like mantle feathers have been acquired) these were pretty straightforward to assign to category. Below are the only second- and (presumed, by black in the bill and small apical spots) fourth-winters I managed to photograph.

Also, as with Slaty-backed Gull, I left with confused as to how to identify first-winters with certainty. I was actually finding it difficult to find first-winters (or at least ones in 'easy' spots), which alone told me I must be overlooking the majority of them (as adults were abundant). My Gestalt of a first-winter was clear at the outset: It should be pale on its head (with perhaps a few streaks around the eye and no smudgy mask); it should have 'patterned' scapulars; it should have a crisp 'piano key' pattern on its greater coverts; it should have fresh tertials with notches in them; it should have a patterned base to its tail (plain tails would be 'out'); and it should be slimmer, 'fresher' overall, and longer-winged than Slaty-backed Gull, with black-looking (not brown) primaries. I found a handful of birds which fit with my Gestalt comfortably, and identified these as 'good' Vega Gulls.

However, as with Slaty-backed Gulls, there were others which seemed to show a mix of characters, and these quickly undermined what faith I had in both of my 'Gestalts'! It was becoming clear that there was overlap in the features I had earmarked as being indicative of one form or the other, and the problem was that I had no idea which should take precedence when I found both in one bird. Below is one such problem bird, which I identified initially as Vega Gull by its well-patterned scapulars, pale and patterned upperwing coverts, tertials with notches in them, and overall strikingly 'patterned' appearance. However, I switched to Slaty-backed Gull due to smudgy (brown) markings on its head and body, short thick bill, and wavy (rather than 'piano key') pattern through its greater coverts. Once it spread its tail I was immediately back to Vega Gull again, as its tail band was actually quite narrow, with a very intricately patterned base! As I look at the photos now, I'm back to Slaty-backed Gull again! So which is is? Is it a fresh-looking Slaty-backed Gull with some Vega-like characteristics? Or is it a dark and smudgy Vega Gull?

My only flying first-winter Vega Gull arguably has a similar set of problems with it, as its greater coverts become more uniform towards its outers and its scapulars are broadly dark-centred and quite plain (the same pattern as on one of the 'question mark' Slaty-backed Gulls in the previous post). However, I'm sticking with Vega Gull on account of the patterned (not solid) look to the underwing coverts, the intricately patterned tail, and the overall freshness of the entire upperside.

My conclusion to this post, then, is identical to that of the previous one: i.e. that I'm not entirely sure where the boundaries between Slaty-backed Gull and Vega Gull lie and which identification criteria should take precedence in individuals which appear to show a mix of characters. Although I was very happy with my trip to Choshi, this was the one big let down, and I could have done with at least a couple more days of head scratching available to me to have spent trying to figure this out! Above photos taken at Choshi Harbour, Chiba Prefecture 6-9/2/18.

Monday, 19 February 2018

Choshi (4): Slaty-backed Gulls

I had a myriad reasons for wanting to visit Choshi: Get Thayer's Gull Larus thayeri; get Glaucous-winged Gull Larus glaucescens; see thousands of East Asian gulls close up; photograph the various cormorants; and so on and so on. In all of these departments, I would have to say that the trip was an overwhelmingly successful one! One of the key reasons for going there, though, was to take a closer look at Slaty-backed Gulls Larus schistisagus, specifically to try and figure out precisely how first-winters differ from same age Vega Gulls Larus vegae as the separation of these two had been causing me problems back in Taiwan. In this regard, I can only conclude that the trip was a failure as I left very much 'none the wiser' (if anything, even more confused). Starting on a positive note, though, adult Slaty-backed Gulls pose no identification problems whatsoever and are a marvellously attractive species, with their disgustingly dirty heads (in some) and striking string of pearls in flight. Attached are a few representative examples of this cracking gull.

Second- and third-winters, too, are a straightforward proposition to identify, as they are both pale-eyed and sport either some or a majority of adult-type dark greyish feathers in the mantle. Something about the structure (of many, but note already that the first individual above is uncharacteristically 'leggy'), 'mien', and general appearance is also quite distinctive.

The distinctive look of older Slaty-backed Gulls is also reflected in many first-winter birds, and the first few I encountered at Choshi are shown below. These are all obvious birds, with slightly drooping, short, thick, blackish bills, somewhat 'fluffed up' thickish/swollen-looking heads and necks, smudgy/dusky 'masks' around the eye, washed out/faded (and short) rear ends (tertials and primaries, either brownish or 'frosted-looking', creating a 'patchy' look to the upper primaries on the open wing), and similarly faded and patchy-looking plain tails with diffuse and faded-looking white terminal 'areas' rather than neatly defined narrow white fringes.

So far so good, but the seeds of subsequent problems are there to be seen in just these first few individuals. Firstly, the pattern of the scapulars is different on each bird, including 'juvenile-looking' ones with largely dark centres, 'juvenile-looking' ones with dark anchor marks distally, bleached and faded ones with indeterminate markings, and more 'adult-like' ones with blue-grey centres and fine shaft streaks. The greater coverts vary in a similar way, as do the tertials, with even the suggestion of Herring Gull-like 'piano key' patterns through the greater coverts and pale notches on the tertials of one bird. The only thing these four (perhaps five) individuals have in common is that they are all bleached or worn on their outer wings and tails. Elsewhere, there is variation, even in these first few 'obvious' first-winter Slaty-backed Gulls. Imagine my horror when I ventured further into the harbour to be greeted by this lot, all of which I presume to be Slaty-backed Gulls!

The last bird above is a confusing one as it has well-patterned scapulars and a 'piano key' pattern through its greater coverts. It is not especially bleached or worn, though it is bleached through its primaries and on its uppertail. This, together with the smudgy eye mask, suggest that it is Slaty-backed Gull rather than a Vega Gull. But what about these next few birds? The first is strongly patterned through its wing coverts but does have a smudgy face, plain centres to its scapulars, and rather plain tertials (so Slaty-backed Gull). The next has the 'oily-blue' cast of a Glaucous-winged Gull Larus glaucescens to it, but has a rather dark saddle and is very bleached and worn through its entire wing (so Slaty-backed Gull). The last one is perhaps the most confusing of all, as it seems not worn in the slightest and even appears rather long-winged. However, the broadly dark centres to the scapulars and the greater coverts would suggest that it cannot be Vega Gull. I saw one or two birds that looked like this one, and photographed one flying. These didn't look much like the other Slaty-backed Gulls around, even though I couldn't see what else they could be!

I left Choshi with far too few spread wing shots of this species, distracted by all the other (newer) gull species present there. Those that I did get show the same kind of variation as do the standing birds, leaving me wondering just what a 'typical' Slaty-backed Gull ought really to look like! The first bird below is an excellent approximation of my pre-visit Gestalt, with its extensively bleached upperparts except for a smudgy eye mask and a darker belly. The second bird is close, too, with its mostly black tail (though note some white at the base of R6), faded 'hand', and 'Venetian blind' effect through its outer primaries. The third bird is similar but has a more densely barred rump than I would have expected. The fourth bird is similar to the others, but note has Herring Gull-like inner primaries, with arrowhead tips on P1-4 and large pale rectangular areas in the outer webs of those feathers. I assume it must be Slaty-backed Gull due to its evenly dark greater coverts, as I do the fifth bird, which (unlike the others) has some worryingly complex barring on the base of R6!

So, 'as clear as mud' is the conclusion I have arrived at having failed miserably in my quest to isolate precisely how first-winter Slaty-backed Gulls differ from same age Vega Gulls. I assume all the birds pictured above to be the former, though cannot rule out having misidentified one or two. Whilst a large number of Slaty-backed Gulls are really quite obvious, others seem to be able to show one or more pro-Vega Gull features (arrowhead markings on the scapulars, piano key markings through the greater coverts, complex barring on the base of R6, fresh-looking plumage, and so on) in combination with pro-Slaty-backed Gull ones. I could have done with perhaps another day or two to look more closely at these things, but also wonder whether or not that might only have made matters worse! Above photos taken at Choshi Harbour, Chiba Prefecture 6-9/2/18.