Tuesday 3 May 2016

Black-faced Bunting: different looking males

I usually see a few nominate Black-faced Buntings on off-shore islands in spring. They always strike me as pale and uniform compared to personata (Masked Bunting), the local taxon. When I was out on Hegurajima last month I came across these two males.

I managed to get a few shots of the first bird before it flew deeper into the coastal scrub where I happily left it, keen to make the most of my short time on the island. It was only when I found the second bird that I was struck by how very different they looked. Again I only managed a few shots because of time pressure but now it was me that had to disappear as the ferry was about to leave.

The northerly breeding nominate spodocephala is the passage taxon in Japan, the more southerly breeding sordida must have very limited spring overshoot potential and it hasn't been recorded in
Japan according to the most recent official OSJ list. 

Buntings and Sparrows (Byer's, Olsson and Curson - 1995) states, "Populations from extreme eastern Siberia are slightly smaller, with belly deeper yellow and demarcation between grey breast and belly more ill-defined, sometimes separated as the race extremiorientis. Some authors treat north-east Chinese and Ussuriland populations as part of the race sordida.". There's no mention of extremiorientis by any of the widely followed authorities as far as I'm aware but I can't help wondering if these two individuals could be representatives of the two populations whatever their taxonomic status might be.

The first bird...

The second bird...

After quickly posting this earlier today I'd like to add a little more.

I considered age as the reason for the differing appearance but as care is needed separating 1CY birds from adults after the post juvenile moult I doubt they'd become easier as they all become more worn in spring. Nevertheless this may still be the case.

Points of interest comparing the first bird with the second:-
The most eye-catching is the very bold flank streaking along with streaks on the centre breast.

The greater primary coverts seem tipped whitish compared to the more uniform brownish fringes of the second bird.

Is the primary projection really longer and spacing of the outermost primaries different? It looks as though there could be a missing tertial creating the longer projection but this wouldn't account for different spacing. If the tertial is missing this must be accidental loss as there shouldn't be any moult of major feather tracts at this time. I'm unaware of any difference in primary length between any of the races so this probably meaningless.

The different face pattern. The difference in mask shape may simply be due to the timing of pre-breeding moult and how many feathers on the face have been replaced.

Some additional images...

These heavy crops show the primary grouping and in the final shot apparently the full complement of tertials.

Greater coverts with brownish tips very nearly concolourous with the fringes. Clean breast and minimal flank streaking.

All along I'd been thinking it was the first bird that was the oddball but after posting this I went through my old images of spococephala and realised it was the second bird that doesn't fit the usual appearance. Here are images of a couple more birds I've seen in the past, the first in early May and the second an October bird.

A May 6 bird on Hegurajima, less boldly streaked on the flanks but otherwise very similar.

A fresh male in early October with a female personata below. Is it smaller? Is the bill smaller?

A spring personata to round off.

Now I'm getting turned around and I'm wondering whether the first bird is typical example of the north-east Asian population and that the paler, more uniform bird could be a rarer visitor from further west. Apparently there is a cline with paler birds in the west and darker birds in the east.

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