This image from Bahrain in early March 1999 (Martin Reid) provides
a valuable comparison of the three main taxa of large gull that
winter there; they are (from left to right):- barabensis,
heuglini, cachinnans (probably the eastern nominate
form, not the paler western ponticus). The relative
size and structure is typical for most birds seen there, and demonstrates
my personal experience that heuglini is in-between barabensis
and cachinnans in size. The fourth - or rightmost - bird
is most interesting, as it has quite extensive fine streaking
on the rear crown and nape, despite the bill appearing to be fully
adult-like. Combine this with a pale eye, an apparent mantle shade
inbetween barabensis and heuglini, fleshy-yellow
legs, and an angular bill/forehead shape, and I feel we may have
a Big Pale Heuglini-type here, despite the apparent small
size (thus perhaps a female?). I am keen to entertain
other possibilities for this bird - thank you:
