Kent Ornithological Society 
The Kerton Stonechat © Terry Laws
In November 2016 a rather strange looking Stonechat appeared in the coastal gorse scrub along Kerton Road, Dungeness. The bird was rather pale, greyish and without any of the warm ochre or fawn tones associated with this species in most plumages. It was a puzzle, but given the time of year and the general pallor it began to be described in the birding social media as a ‘Siberian Stonechat’, even though most of the earliest observers were by no means convinced of that attribution.
Inevitably given the impact of social media in modern birding, this little bird attracted a good deal of attention, so on 11th November on one of my infrequent visits to Dunge I decided to take a look, especially as it seemed to be associating with a Dartford Warbler. It was a rather grey day, but I found both birds and managed to make some rather simple sketches during about 15 minutes’ observation. It was a little charmer, but I could not reconcile what I saw with my prior experience of Siberian Stonechats of the race ‘maura’, or the Common Stonechat which is frequently encountered within the UK. Its general lack of warm tones vaguely reminded me of the juvenile plumage of the Ethiopian race ‘albostriata’, but even that seemed to be only a passing resemblance. I felt puzzled and intrigued, but also fairly sure this was not a typical Siberian Stonechat. This trend began to grow within the birding community, especially online. I planned to make another trip to make some more sketches, hopefully in better weather, but fate took a hand and I sustained an injury (largely through clumsiness) which prevented me birding in the field for the next three months!
The Kerton Stonechat © Barry Wright
The Kerton Stonechat © Barry Wright
Without my involvement events progressed rather well; faecal samples were collected and despatched for DNA analysis and the birding world waited, possibly with baited breath. When the answer came, it was a bit of a revelation, confirming the identification as a bird of the far-eastern race known as ‘Stejneger’s Stonechat’. This was pretty big news, as this taxon has only recently been recorded in Britain and its field identification is still to some extent in a state of flux. Even so, many observers, myself included, found this identification extraordinary as the bird did not show most of the key characters we would expect this form to show.
In the birding social media, however, this was a big event and substantial numbers of birders travelled to see the ‘Kerton Stonechat’ mostly because of the potential for it to be split in the future and be confirmed as a separate species in its own right. However, ‘all was not well in the state of Denmark’ and a growing sense of confusion led to the re-testing of the faecal samples, which re-assigned the bird to the Common Stonechat!
Kerton Stonechat © Peter Maton 
Normal Stonechat © Nick Smith
The response online was a little surprising, with frustration, scorn, disbelief and ridicule in fairly equal measures. However, what struck me was the extent to which it revealed the lack of understanding of the application of mitochondrial DNA analysis. By an odd coincidence British Birds magazine had included a very thorough explanation of the use of this process in bird identification in a recent issue. This should have been helpful, but perhaps not too many people had read the article, because some of the discussions online showed the extent of the misunderstandings, with some asking ‘how could the DNA change between samples’ to others pouring scorn on the applicability and reliability of the technique based on little evident relevant expertise. When the truth came out it was somewhat re-assuring to find that the initial, incorrect, identification as ‘Stejneger’s, was the result of good, old-fashioned human error. The lab contained samples from a real Stejneger’s also undergoing analysis, and the samples were inadvertently confused
So interest in the Kerton Stonechat ended abruptly as the peripatetic birding community found new prizes to pursue. This to me was a bit of a shame. This little bird was still intriguing; now we could be reasonably sure it was indeed the Common Stonechat we all know and love, why does it look so different? The most likely answer is that it represents a plumage mutation which is not that common.
The Kerton Stonechat; this fine photo shows many of the plumage features but also demonstrates the effect of light on the plumage, which appears somewhat warmer in tone than the bird seemed in other photos and in life © Moi Hicks
There is an interesting record on the Bird Guides website of an aberrant Robin in Devon, which lacked all the orange, yellow or olive colouring.
Hein van Grouw, Senior Curator at the Natural History Museum, Tring, commented on this Robin: "The pale colour is the result of a mutation which causes the dilution of both pigments (eumelanin and phaeomelanin; Robins do not have carotenoids), so it is not leucism as suggested in the photo captions. The phaeomelanin seems to be diluted stronger than the eumalenin, but is not fully absent as the forehead and breast still have a pale, cream colour. Robins with this colour are seen more in Britain, so clearly the gene for this type of dilution is present in the Robin population. I have even seen evidence that they do breed with normal-coloured individuals, so perhaps the orange breast colour in Robins is not so important in the mating process after all… I often call the dilution of both pigments 'Dilution Pastel', while the reduction of eumelanin alone I call 'Dilution Isabel'.
For more information on plumage aberrations read:British Birds Vol.106; 2013 17-29 “What Colour is That Bird? It seems highly probable that the Kerton Stonechat was exhibiting a similar plumage aberration. At the same time as this bird appeared at Dungeness another very similar bird was present in London and another was reported from another site in southern England. Lee Evans commented” …. these grey variants are not that rare and crop up from time to time – I have seen quite a few over the years”. There is some evidence to support the view that young Stonechat siblings dispersing from breeding areas in northern England can winter in similar localities, so perhaps all the ‘grey stonechats’ recorded this winter were from one brood.
Norman McCanch