This post poses more questions than answers, but you’ve gotta love Yellow wagtails
The first bird of interest was photographed recently by Nick Senior at Grafham Water in Cambridgeshire.
This bird shows grey upper-parts/nape/crown that perhaps could be explained away by individual variation or perhaps that old chestnut ‘within acceptable variation’ (birds similarly plumaged to this are observed most springs) However the wing-bars are possibly not what we would expect to see. They are both broad and distinctively white, reminiscent of those shown by Citrine Wagtail. Can flava Yellow Wagtails show wing-bars like this?
Perhaps as significant is the call. Nick transcribed the call (in his own words) as a bzzslpp’ similar to typical flava though more complex and lower toned with an almost bunting (eg Reed) type quality. A recording of the call could perhaps prove very valuable in untangling the conundrum?
I recently observed another interesting Yellow Wagtail at one of the few regular breeding sites for this species in North Cumbria. This individual showed a grey colouration to the mantle that extended up onto the nape and crown. There also seemed to be contrast between the apparently brighter yellow tones on the face and the more washed out yellow on the breast. The median covert bar also seemed to be bright white and perhaps broader than I expected (though admittedly not particularly obvious in this image)!
My assumption at the time was that this bird was just a variant flavissima, and this may well be correct. However, where does this apparent ‘citrine-esque’ ghosting come from? Is this just variation? Could there some other influences leaking into this species genetics or are these individuals originating from a distinct population?
Toby Collett has observed similar birds to this at the Saltholme RSPB reserve in Cleveland over the previous few years. He has also observed that the calls seem ‘buzzier’ than those of typical flavissima. The following youtube clip recorded by Toby shows a very similar bird to the Cumbrian bird, though perhaps more importantly, you can hear the bird calling.
The call is (to my ear at least) different enough to warrant further analyses; so some recordings of these ‘grey-types’ could be very interesting.
It seems that these grey-types may be a regular feature in the UK, particularly across the east coast of the UK. However it would be interesting to discover more about these birds! It may be that they are just a variant of flavissima, but there could still be lots to learn……