I may be onto something 16 0ctober 2012

The main criteria for distinguishing adult from first winter Purple Sandpipers is given in reference books as the  difference in shape, colour and patterning of the lesser and median coverts on their wings. Adult birds have square ended  lesser and median coverts with diffuse grey fringes which provide little contrast whereas first winter birds have rounded tips to the lesser and median coverts with prominent white fringes providing a marked contrast and scaly appearance to the closed wing, much different to adult birds. 

The following images are ones I took of both first winter and adult Purple Sandpipers in early winter at Brixham where there is a regular wintering flock. Note the difference in colouring to the legs, feet and base of the bill of  first winter birds compared to adults. The first winters show bright orange legs and feet combined with a reasonably extensive orange base to the bill whereas  adults have duller greenish yellow legs, feet and base to the bill. The colouring on the bill base of the adult also appears to be less extensive. The difference in colouring of the bare parts was very obvious at the time and appeared to be consistent amongst the seventeen individuals present on the rocks. This feature was easier to use than the wing covert patterning to distinguish between the two ages. I cannot find any reference to this difference in any reference book including BWP but it may be worth using when next a Purple Sandpiper turns up in Oxfordshire or anywhere else you are lucky enough to encounter one or more. Please note this observation was in early winter and as the winter wears on there maybe changes in the bird's plumage and colouring but it certainly seems to work for the period before January of the following year

First winter Purple Sandpiper.

Note the orange legs, feet and bill base combined with the retained juvenile lesser and median wing coverts showing rounded tips with prominent white fringes

First winter Purple Sandpipers

Adult winter Purple Sandpiper. Note the dull greenish yellow legs, feet and bill base combined with the diffuse grey fringes to the square ended lesser and median wing coverts showing much less contrast than on first winter birds

Adult winter Purple Sandpipers