I'm sure there's an explanation for this, but I don't know what it is.
No interactions present.
It does seem to happen towards the end of the breeding season and the bird guides do mention this. I guess like other species, the 'hard parts' colour varies depending on 'hormones', which vary in individuals as well as during the year?
Alan Brampton (Benson)
Thanks for that. I shall squirrel that bit of information away for future use...
Lat/Lng: 51.7987, -0.0053
OS grid ref: TL376129