Phil Tizzard raised the question of ageing Northern Wheatears in the UK in autumn. This is far from easy in the field, particularly with females. I’ve always thought that adult (winter)males exhibited a plainer, darker wing with less obvious feather fringing than juvenile/first-winter males, which is why I would have been inclined to have aged the Stanford individual as a juvenile/first-winter had I seen it in the field. It appears, however, that this is far from clear cut. According to Svensson (Identification Guide to European Passerines), the only infallible criterion for ageing these birds is the colour of the inside of the upper mandible, which is yellow in juveniles/first-winters as opposed to grey-black in adults. This means that attempting to age autumn Northern Wheatears in the field could be very tricky! The Stanford individual had a yellow inside upper mandible and so could be aged confidently as a first-winter (or, if you like, ‘older juvenile’). Here is another photo of it with its wings closed. Note how the upperparts appear greyer here than in the image in the previous post.
I like a challenge so I will be paying a lot closer attention to autumn Northern Wheatears in future … Thanks to Phil for bringing this up and to John Cranfield for helpful comments.