Siberian Stonechat age and race

Hoswick, Shetland, October 2012

by Martin

Stunning bird and one that has become much rarer in Britain. Only 2 British records in 2011! I saw this one 3 times and all of our 2 groups got it. It raised some question for me too:

a) Most are assumed to be West Siberian ‘maurus‘. However recently East Siberian ‘stejengeri’ was found to be in broad terms genetically distinct. It is also a potential vagrant. So ‘Stejneger’s Stonechat’, a potential new species and hidden West Europe Vagrant?
b) This Hoswick bird is clearly a male (black underwing coverts and black feather bases on throat etc.) But how easy is it to age? Adult or first winter?

Especially Roger R and I thought first winter but not easy so also checked with Magnus Hellström (see his comments in red italics below):

Yes Martin, you are right. This is indeed a first winter male. Unfortunately  the photos does not show any moult contrast to back this up (at least, I can’t find any), but in my view the ageing of this individual is still safe for the reasons outlined below.
 Juvenile maurus has partial moult during late summer. This moult seems to be on average more restricted than in rubicola (and also than in stejnegeri) and, apart from the body feathers, many individuals apparently include no more than the lesser coverts. Hence, in many birds the moult contrast is very hard to spot in the field. Perhaps your individual fits this pattern, but to be sure we would need an in-hand examination.

Still, there are other age-related characters assessable in the photos. Firstly, the primary coverts show a typical first-winter pattern with pale buffish edges, typically widening to a broader (and slightly diffusely set off) tip. In a folded wing, the broad pale tips almost blur into each other, hiding most of the darker parts of the feathers. In adult (2cy+) birds, the pale edges are typically whitish, narrower, more sharply set of against the black feather centre, and does not widen towards the tip. This character is applicable in most autumn individuals, but a few birds may be somewhat harder to assess. The Shetland bird looks typically first-year in this respect. Secondly, 2cy+ maurus shows a more (usually much more) well developed head pattern than first winter birds. The situation is rather comparable to autumn males Common Redstart, with adult birds showing a quite well developed black throat bib and, more importantly, jet-black lores. First winter males are extremely variable, showing anything from a completely female-like throat and face pattern (including pale feather bases) to a rather adult male-like one, but still dominantly or partly covered by pale fringes. Intriguingly, many first winter birds show a patchily developed pattern with only parts of the ear-coverts or throat having black feather bases, while other parts having pale bases. The Shetland-bird clearly shows a first-winter pattern, and my guess would be that a thorough examination would prove this as a patchily developed individual. 

The separation from rubicola is straight-forward in the Shetland bird, they key characters being jet-black axillars and underwing coverts (the former with fresh pale fringes) and upper tail-coverts lacking dark rubicola-spotting. It should also be noted that in rubicola, first winter males are generally harder to separate from 2cy+ males, since (contrary to maurus) first winter plumage shows a better developed throat and face pattern.

1st cy male Siberian Stonechat, apparently ssp. maurus.Hoswick, Shetland, October 2012.

Safe separation from east Siberian stejnegeri is trickier, and is generally not possible in single individuals. On average, stejnegeri in fresh plumage is a somewhat darker bird with a warmer colour scale, less developed neck patches and a smaller white/ochrous rump pattern.  The Shetland bird does look typical maurus-like, and imo gives no actual reason for suspecting stejnegeri.

adult male Siberian Stonechat ssp stejnegeri. NE China, Sept.

In contrast to first winter birds, 2cy+ males (here illustrated by a stejnegeri) typically show jet-black lores and primary coverts with distinct, thin and white edges that does not widen towards the tip.

My first group, watching this stunning Siberian Stonechat. Beautiful scenery, great company, rare bird and no one else around.

and of course it was a new bird for some- so our hidden X was released!

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About Martin Garner

I am a Free Spirit
This entry was posted in Chats and Thrushes, Shetland. Bookmark the permalink.

4 Responses to Siberian Stonechat age and race

  1. Tom van der Have says:

    The picture above of a stejnegeri from China shows very well another known character of stejnegeri: the broad(er) base to the bill. In fact, it really looks like a barn swallow! Would be good to check the single British record, first accepted as stejnegeri, later changed into maurus/stejnegeri for this character.

  2. Jan Jörgensen (JanJ) says:

    Thanks to Magnus for a comprehensive explanation (as usual), of the characters for the Shetland.
    bird. Wouldn´t the tail feathers be a reasonable good pointer to a first winter bird with pointed and slightly worn tips. Also the dark ends fairly poined towards and inside the pale tip.

    JanJ

  3. Pingback: Stejneger’s Stonechat in the Netherlands? | Birding Frontiers

  4. Pingback: Stejneger’s Stonechat in Korea: A Quick Introduction with Images « Birds Korea Blog

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