Thursday 25 October 2018

A Contentious Stonechat 23rd October 2018

Until comparatively recently the Siberian Stonechat has comprised of five subspecies but only two need to concern us here, Saxicola maurus maurus which occurs west of Lake Baikal and S.m stejnegeri which occurs east of Lake Baikal.The two subspecies are virtually indistinguishable, with stejnegeri said to be darker and more saturated in plumage tones although this can be highly subjective.The only real way to tell them apart is mitochondrial DNA analysis, using a feather or faecal sample although even this has proved to be contentious. These two subspecies of Siberian Stonechat cover a vast area stretching from Russia in the west to Japan in the east and vagrants regularly occur in Britain each year, chiefly in the late autumn.

Recently the two subspecies have been found, after mtDNA analysis, to not be as closely related as was suspected for many years but that stejnegeri is more closely related to another species of stonechat, African Stonechat Saxicola torquatus, than to Saxicola m maurus the other sub species of Siberian Stonechat with which it overlaps in its distribution where they come into contact.

The BOU (British Ornithologists Union) decided to follow, from 1st January 2018, the IOC (International Ornithological Congress) recommendations concerning recognised bird species and what names should be applied to them.

The IOC decided, based on results of the mtDNA analysis carried out earlier, that the subspecies of Siberian Stonechat called stejnegeri should henceforth be classed as a separate species of stonechat called Stejneger's Stonechat Saxicola stejnegeri leaving Saxicola m maurus and the remaining other subspecies to be called Siberian Stonechat.

If you have not already lost the will to live the relevance of all of this is that Stejneger's Stonechat, being recognised as a species separate to Siberian Stonechat (its former designation) has now become much desired by twitchers and anyone else interested, nay obsessed, with seeing as many British bird species as possible.

The first  Stejneger's Stonechat to be identified in Britain was one at Portland near Weymouth in Dorset in 2012 and originally accepted, after a DNA analysis of one of its feathers as a Siberian Stonechat of the sub species Saxicola m stejnegeri. It has now, as a consequence of the recently accepted IOC taxonomic changes,  been retrospectively promoted to Stejneger's Stonechat as of 1st January 2018.

A stonechat, inhabiting reeds, brambles and ditches near Salthouse on the north Norfolk coast for the last few days has been causing quite a stir as, although it is irrefutably a Siberian Stonechat, it appears to be quite dark for a Siberian Stonechat S.m maurus and is being proposed as probably a Stejneger's Stonechat, although this is purely speculative*

* see the end of this blog for the latest update

Many birders have come to twitch  it, just in case, but it is virtually impossible to distinguish Stejneger's Stonechat from Siberian Stonechat on plumage features observed in the field. Some suggest that Stejneger's Stonechat has darker brown fringes and colouring to the mantle and scapular feathers on the upperparts, or a more saturated rusty tone to the rump and upper-tail coverts but this can vary enormously with light conditions and the angle from which the bird is seen. Others claim a less well marked supercilium is an indication of stejnegeri but this too can vary amongst individual birds. Nothing can be claimed to be really definitive at the moment from observations made in the field and then there is always the area of inter-gradation to be considered where the two species breeding areas overlap*

The alternative is either to capture it and examine it in the hand, which still can prove problematic or to take a sample of a feather or faeces for mtDNA analysis.

*Further reading on identifying Stejneger's Stonechat can be found in the following: 
 Birding Frontiers, CHALLENGE SERIES AUTUMN by Martin Garner published 2014  pp 126-127.

A faecal sample has been obtained from this bird and sent to Dr Martin Collinson at Aberdeen University for analysis and now everyone is waiting to see if they can add Stejneger's Stonechat to their list.

I went to see this contentious stonechat today as Hugh, a good friend who works for the Environment Agency, was giving a lecture at the UAE (University of East Anglia) in Norwich and then planned to come and see the stonechat on his way back home, never having seen a Siberian Stonechat in Britain, let alone a Stejneger's Stonechat. Not having seen Hugh for some time, I could combine a reunion whilst checking out this stonechat that is attracting so much attention

We arranged to meet at noon but not relishing the rush hour traffic on the long tedious drive to Nelson's County I was in Norfolk much earlier and found myself at 9am wandering up a track called Meadow Lane, between a reed filled ditch on one side and a grass bank topped with brambles bordering a field on the other side. It was not far to walk, just a few hundred metres, and the wind created a pleasant, soothing sound as it shook the tasselled reed heads into constant motion.

It was obvious where the stonechat was, as a small huddle of birders were looking intently over a gate barring entry to a field of rough grass with a ditch full  of reeds running along its left side

The stonechat was in the green reeds in the ditch to the
left of the picture
The stonechat was immediately visible, perching in the lee of a clump of taller growing reeds and by a leaning fence post in the ditch, sheltering from the worst of the strong westerly wind that was gusting unhindered across the surrounding open grassland.

It was very obvious how much paler this stonechat was than our native European Stonechat, its chin and throat were pure white, its upper-parts greyish brown rather than dark brown and its pale underparts suffused with a peachy orange blush. Its rump was noticeably paler than found on a European Stonechat and a slightly richer peach orange than its pale underparts and totally un-streaked - a diagnostic feature of Siberian or Stejneger's Stonechat. This individual appeared to be a male as its under-wing coverts and axillaries were pure black, yet another diagnostic feature of Siberian or Stejneger's  Stonechat.

Not the greatest photo but it clearly shows two of the 
diagnostic features of Stejneger's and Siberian Stonechat, 
namely an unstreaked pale peach coloured rump and black 
underwing coverts and axillaries. The white fringes to the
 tail feathers are also another marked feature
All in all it was a very neat looking and engaging little bird, its tail noticeably fringed and tipped with white as it perched on various stalks or reed stems. It was mainly catching flying insects in the hour I watched it, although it managed to find a few caterpillars and invertebrates on the ground too. Usually it stuck to its sheltered area behind the reeds, only flying out to catch a winged insect every so often but on occasions it perched quite happily on an exposed reed stem, clinging on and swaying violently in the wind..

I watched it for another half an hour but then it was chased off by a male European Stonechat and flew over our heads to perch on some brambles on the bank behind us. It fed from here for a while and then dropped down to feed from the reeds filling the ditch by the track before flying back to its original position in the lee of its favourite clump of reeds.

A huge flock of Pink-footed Geese, cackling and squealing excitedly, flew over us in a vast wavering scrawl across the sky, wing tip to wing tip, spreading across the azure heavens in a long irregular line. The evocative sound and sight of winter in Norfolk.

Today it was bright and sunny in this unseasonably mild, autumn weather but the days are shortening and soon enough winter will be upon us and life will get harder for both birds and mammals.The weather is predicted to get much colder and windier in the next few days and I cannot but wonder if the contentious stonechat, in its windswept ditch and still the subject of much conjecture, will remain or head for warmer climes.

*Update 17th November 2018

The mitochondrial DNA analysis of a faecal sample obtained from this Siberian Stonechat has established that it is indeed a Stejneger's Stonechat. This is good news for me and many others who made the effort to see it as it means we can add another bird species to our respective lists of bird species seen in Great Britain

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