When I think of September birding in Cornwall there is one area that always excites me in it's birding potential; the classic site of Davidstow Airfield. This amazing abandoned airfield has a phenomenal track record for American waders and seems to produce rarities like clockwork each autumn, despite it being well watched I'm usually lucky enough to find at least one of these every year with 2019's adult American Golden Plover being my last decent find there. Sadly 2020 hasn't been easy for me to check this area as I have been working in other parts of the county and also continuing to push for my ringing permit but out of just four visits me and Libbie did pretty well in what seems like a poor year for Davidstow.
Our first visit on 10th August produced a lifer for Libbie and a new wader for the site for me in the shape of two immaculate juvenile Wood Sandpipers which dropped in to the pools by the control tower all too briefly before presumably flying off to Crowdy.
A write off trip before work in the fog when I had a day's work in Wadebridge left me ruing my choice of getting out of bed at 6am (!) and then I almost had to forget about the place for the time being. Fast forward to 22nd September and with rain all day and work sending me close by I decided on a quick trip to Davidstow in the evening with Lib. As I hunted for waders Libbie found a funny Yellow Wagtail within a group of Pied and White Wagtails and asked me what it was? Now I usually can sort out Yellow Wagtail to sub-species or at least make an educated guess by noting several features and building an identification by a process of elimination but this bird had me stumped.
The dark looking head, even darker ear coverts & 'cold' green mantle made me think of Thunbergi but it had a thin supercilium which was yellow in color, The bird then flew across the road calling as it went (much more raspy than standard UK *Flavissima call). From then on I decided to write some field notes and take plenty of pictures in the hope of sorting it out after the event. Photographs below are unedited.
The thin yellow supercilium, dark headed appearance with even darker ear coverts and yellow wash to the white throat patch didn't point firmly to any sub-species I was familiar with.
Note the contrast to the greater coverts with the juvenile retained outer feathers looking faded and white in comparison to the fresh buff tinged (adult type) inner greater coverts. Ageing this as a 1st winter. Body moult has already progressed more than would be expected of an Eastern Yellow Wagtail which would be typically grey and white and in more juvenile plumage. The brightness of the overall plumage and amount of yellow already moulted through would suggest it is a male.
The greenish upperparts had a distinctly cold grey tinge especially on the mantle. Differing somewhat to the brighter green tones of Flavissima or Flava. Pointing perhaps to an eastern origin.
|This head on shot shows the striking head pattern well with dark grey head, broad well defined ear coverts which were even darker than the rest of the head plus white throat with yellow suffusion. Note the thin yellow supercilium.|
This image shows the very subtle 'necklace' on the bird's breast.
So it would appear that the Davidstow Wagtail is an intergrade between two more well recognized sub-species. In my opinion it surely has some * Feldegg genes owing to the dark headed appearance and what sounded to my ear a raspier flight call than typical Yellow Wagtail. However the darker ear coverts, prominent supercilium and obvious lower eye-ring point towards some * Flava influence or perhaps more likely in my opinion * Thunbergi as the subtle necklace on the upper breast is an often quoted feature of this subspecies. These intergrade Wagtails are often named as 'Dombrowskii' or 'Superciliaris' are commonly found migrating in the eastern Mediterranean in Greece and Cyprus during the spring and autumn migration and occur in Romania during the breeding season. My bird would appear to fit Dombrowski better.
Whilst it would be pushing the boat out a bit to be 100% sure on a 1st winter bird in the autumn I feel that it would be too easy to not at least try and work out any interesting Yellow Wagtail's we see during Autumn in the UK. This is a constantly evolving species group and I am sure that birders and ornithologists alike still have much to learn about their plumage's and identification. It will get you ready for nailing the ID of future birds and also help you identify Citrine Wagtail or perhaps Eastern Yellow Wagtail by looking that little bit more thoroughly.
* Flava - also known as Blue-headed Wagtail, the nominate race in mainland western Europe. A scarce but annual passage migrant in Cornwall which has bred on the Lizard Peninsular.
* Thunbergi - also known as Grey-headed Wagtail, the Scandinavian subspecies of Yellow Wagtail. A rare passage migrant in Cornwall.
*Feldegg - also known as Black-headed Wagtail, a distinctive subspecies of Yellow Wagtail breeding in the Balkans east to the Caspian Sea, south to Turkey, Iran and Afghanistan.
Further Reading: Pipits and Wagtails of Europe, Asia and North America by Per Alstrom and Krister Mild.
Thank you to Kester Wilson for originally suggesting the ID of Dombrowskii whilst I was still fairly clueless and to Peter Roseveare for his research into the matter.