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| Male Yellow Wagtail at Clifton pits of the UK standard flavissima subspecies |
I visited Clifton pits again today where I spent most of my time watching and photographing the Yellow Wagtails.
The Yellow Wagtail complex is a challenging one, being similar in complexity in many ways to Gulls. It is a highly polytypic species meaning that the members of the classification can be divided into many subspecies which are typically geographically differentiated. There are at least 15 subspecies recognised which are mainly differentiated by the head pattern of adult males in summer plumage. Ten of these are depicted in the Colins bird guide bible. Here you can see the head pattern variation from the common UK form, flavissima, through shades of grey and blue to the almost black head pattern of the form feldegg found in the Balkans. The identification of the individual subspecies is made even more challenging by the existence of many intergrades between the recognised subspecies. In essence the variation in adult male head plumage is a continuum without discreet boundaries. Any Yellow Wagtail with a blue or grey head pattern is hence of interest to the UK birder. Indeed several suspected Iberia subspecies have been reported in the UK this spring. The most frequently found variant in the UK is the so called Channel Wagtail which is an intergrade flavissima x flava. To make matters even more challenging it is almost impossible to assign a subspecies to some first winter birds with duller olive brown plumage without DNA analysis. The much rarer Citrine Wagtail in first winter plumage is also somewhat similar to first winter Yellow Wagtails but can usually be differentiated by the presence of two broad white wing-bars.
Distant record shot of Citrine Wagtail, Shetland, September 2021
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| Channel Wagtail, flavissima x flava intergrade, Farmoor Reservoir, Oxford, April 2016 |
Clifton Pits is blessed with good numbers of flavissima type Yellow Wagtails and there is always a hope that a rare subspecies might also be present. What is obvious from watching the Wagtails at Clifton for any period of time is that there is even considerable variation in the appearance and call of the flavissima type. In the males the yellow breast colouration varies considerably in intensity and the head colouration shows considerable variation both in the shade of olive brown and the shape of the patterning. As far as my birding pay grade allows, I think all the Wagtails at Clifton this morning were the standard UK flavissima type.
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Various flavssima types from Clifton pits this morning. N.B no post shot colour editing has been applied but the white balance auto settings on the camera vary as witnessed by the slightly differ shades of background green.
Recently the Eastern Yellow Wagtail has been split and lifted to full species level. It has a slender and long-tailed appearance and, in general, a bright yellow breast, paler throat and a greyish-olive back. The tail is black with white outer feathers and it often pumps it up and down while walking on the ground. The colouration, as befits the confusion noted above, is, however, extremely variable. It has a diagnostic high-pitched jeet like call. A very long hind claw is also indicative of Eastern Yellow Wagtail. To absolutely tie an Eastern Yellow Wagtail down the diagnostic call needs to be recorded and a DNA sample obtained from poo. Without this they are described as putative. I have seen two Eastern type Yellows Wagtails in the UK, one definitely tickable as it was confirmed by a DNA analysis.
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Eastern Yellow Wagtail, Corporation Marshes, Norfolk, November 2019 |
An excellent paper of the complexities of the Yellow Wagtail group can be found here.
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