Hi Mark,
The heuglini seems dark in the image, fuscus/intermedius like, was that a fact in the field as well?
By the look of it, seems to be a 3rd winter, or an advanced 2nd winter bird, bill looks dark for a 3rd w, but huge variation! It´s moult stage (primaries and coverts) being late, corresponds well with heuglini, or a fuscus for that matter, which can, and has occured in Goa.
Although difficult to se properly in the image (!), it looks like it has two different generation primaries, the inner visible p6, 7, 8 second gen the outer older 1st gen, as the outermost p looks very worn, brownish, and spiky.
However, the broad tertial tips, and the jizz looks good for heuglini, also the extensive
head streaking is possible for heuglini.
The so called 'taimyrensis' (regarded as an invalid taxon, and perhaps more close to vegae, or a hybrid between heuglini and vegae, Yésou. 2002), is paler than nom. heuglini and it´s breeding ground are east of heuglini. It winters in East Asia, but some (uncertain, if- numbers?) said to winter in Indian Ocean and reaching East Africa.
So by the look of your gull, way to dark for 'taimyrensis', and is probably a heuglini.
The two 1st winters could be either barabensis or heuglini, even though heuglini is favoured.
Nice images!
JanJ