Wednesday, 25 February 2015

Dusky Thrush variation

What a difference a camera makes. One great thing for me is being able to turn it on common species and see the kind of detail that I'd probably never have taken the time to discover without being able to scrutinise images. In an earlier post, a couple of weeks ago I talked about a Dusky Thrush that had caught my eye and I'd suspected may have had a touch of Naumann's in its family history, this post is to follow up on that.

There were two or three farmers beginning to plough their fields in Mie when I was last there on 8 February and this provided a good opportunity to look at a few Duskys at close range. From a flock of about 50 birds in one field I was able to get reasonably good images of a handful that came close to my van.

None of the features I though were suggestive of past introgression on the previous bird now look convincing in the light of the variation I saw in this random selection of photographed birds. All the points that caught my eye then could be seen on one or more of the birds on the more recent visit. Indeed a couple of these birds might have made better candidates for showing traits of past introgression but I now feel more inclined to think these features must be within normal Dusky variation. If so then there must be a few Duskys out there that combine most or all of these features and could be confusingly suggestive of an intergrade.

Firstly, no apologies for re-posting old digiscoped shots of an April intergrade in Kyoto a few years ago. This bird is a stand-out example that really doesn't leave any doubt what it is.

Dusky x Naumann's intergrade in April, Kyoto.

Following are images of seven birds that came within camera range, none of them were photographed because I thought they were of particular interest at the time. Two are obviously adult males showing all the distinctive features birders would love to see in a vagrant, one appears to be an adult female and the rest first winters.

Bird one
These shots show an already very smart looking male, not many look as good as this in early February and it was definitely the sharpest bird I saw well that day.

Bird two
This bird has much fresher looking, broad pale fringes still partially masking the bolder plumage of the previous adult male.

Bird three
A first winter with oddly asymetrical tertials. There are reddish feathers on the rear flanks which seems to be normal at this age, though they aren't usually as prominent as on this bird. The extensively brown tail with a rather uniform bright rump and bright tail base look quite like a Naumann's but the blackish longest upper-tail coverts don't.

This bird was photographed in Kyoto city in January 2011 and shows a more typical contrast between the reddish rump and darker tail.

Bird four
Even in dull conditions the proximal three quarters of the tail are brown contrasting with a blacker distal area. In sunlight this brown is surprisingly warm and conspicuous creating the impression of a blackish terminal tail band.

Bird five
This seems to be an adult female and as with the earlier adult males the tail is blacker from most angles. Most birds appear to have blackish-brown markings on the under-tail coverts, if any at all, however this bird is distinctly reddish. Though it doesn't show too well in these jpegs it also has partial reddish fringes along the length of the flanks and more prominently at the sides of the breast. The sides of the neck are also flushed orange to a greater extent than I've noticed on other birds.

Rusty markings on the vent and under-tail coverts plus a few marked fringes along the flanks are unusual.

There are two or three clearly rusty-fringed feathers on the side of the breast and warmer markings across the flanks.

The sides of the neck have an obvious orange flush. Those at the bend of the wing are probably from the under-wing coverts which are in any case orange on Dusky.

Bird six
An odd feature here is the pale dashes on the outer webs of the scapulars, I didn't come across this on any other bird.

Bird seven
This bird looks a nice standard no questions raised first winter.

So there's plenty of variation to be going on with in this small sample, and enough of interest to keep me checking all the birds I see.

Thursday, 19 February 2015

Taimyr Gulls: displaying adults and a Sub-adult, February 8th

The first two taimyrensis I came across in Mie two weeks ago were a displaying pair on the sand flats. For 10-15 minutes they were strutting around calling in unison and are the first and only apparently paired gulls I've seen displaying this winter. Hundreds of Vega were happy just to sit about and enjoy the mild weather.

Later in the afternoon, on a beach where the gulls can be approached more closely, I was able to get better shots of gulls. The following images show a sub-adult Taimyr with an almost a complete black ring around the bill. Originally it was with a small group of gulls, Vega and a couple of first winter Taimyr and I later relocated it in flock of mainly Vega further down the beach.

Sub-adult Taimyr with two Vegas. 

As with the other local gulls, Vega and Slaty-backed, there's a fair amount of variation within saddle colour. By this I don't mean there's a huge difference in saddle colour but that (except for extreme individuals) numbers are evenly distributed along the range of variation. It's difficult to put your finger on what a "classic" saddle shade should be. As can be seen below this bird is slightly darker than the average Vega.

A flock of mainly Vega Gulls. The sub-adult Taimyr is third from the right, behind it is a Common Gull L.c.kamtschatschensis and to its left an adult Taimyr.

A closer view of a yellow-legged adult Taimyr and the same sub-adult again.

The sub-adult in flight.

No doubt it's the hope of every guller to find a so called "classic" if lucky enough to come across a potentially rare gull, well it's certainly mine anyway, and in Japan Vega as by far the most common Herring-type gull is the yardstick to measure the scarce or downright rare against. When it comes to the scarce taxa the slow drip of information means the range of acceptable appearance only slowly reveals itself. Where and what are the boundaries? How many 'good' birds might have to be discarded, how many extreme local birds might blur the boundaries you are looking for? How many "classics" are there in any given population. Oh dear, the usual questions.

By February a small number of Vega have become largely white-headed and lost their prominent grey shawl but most are still streaked to a greater or lesser extent. Some like the the two gulls below are doing their best to keep up appearances and match field guide standards. But many become slightly more difficult to identify and there are always some confusing individuals I'd prefer to forget about if it isn't possible to see them really well.

The following gull is a good example of the latter. It stood out because of its strikingly white-headed appearance. Earlier in the winter anything this clean would immediately suggest Mongolian but more caution is needed by this time. Mongolians from different populations may differ but none I've ever encountered have this wing pattern. The obvious red on the upper mandible definitely isn't something I'd expect to see in Vega, even in breeding condition. It is a little darker-saddled than the Vegas present but the wing tip isn't good for Taimyr either. I wish the bird had hung around but after a couple of minutes it flew off and I didn't relocate it then or last weekend when I visited the same spot. This combination of features is interesting but it'll just have to remain unidentified.

A couple of Vegas on the same stretch of beach.

Mystery white-headed gull with the two Vega and first winter Taimyr. 

Very faint Mongolian-like crown streaking is just visible. 

With adult Vega and first winter Taimyr. The red on the gonys is very extensive, even for Vega in breeding condition. 

The extent of red on the bill and rather dark saddle is an odd combination except for Taimyr which this bird doesn't seem to be judging by the wing pattern. 

The short p10 on the right wing is peculiar. I've seen online images of Mongolian from their breeding range with a mirror breaking through to the tip but it isn't a feature I'm used to seeing on birds here. Perhaps it originates from a different population? Also birds I see here have more extensive black in the outer primaries, both inwards as sub-terminal bands and towards the bases of the outer feathers. 

An old shot of a more typical Mongolian, the p9 mirror is often smaller.

I previously posted on adult taimyrensis type gulls here but focused more on distinctly darker saddled individuals which may actually be misleading.