General description of sub-adult heuglini in March in Bahrain:

Primary moult completed or last primaries to be moulted. Fresh black, with small white tips and with only a small mirror on P10 in 4cy winter heuglini. Primaries adult-like in 5cy winter birds.

Head shape is not rounded and pigeon-like as in many (female) barabensis, rather square or blocky, with a sloped forehead which smoothly continues onto the bill, reminiscent of cachinnans. The thumbprint in front of the eye (common in barabensis) is not obvious in heuglini, the facial expression is dominated by the strong eyebrown, creating a rather vicious look, not unlike West-European Herring Gulls.

Most 4cy birds have a white head with limited delicate neat streaking, concentrated in the lower neck, on some running down to the sides of the breast and over most the area behind and above the eye. The bill is yellow or pink-based with an obvious black bill-band. Often there is some red at the gonydeal angle, but this can be largely obscured by the black markings. Iris is brown-yellow to green or amber.

Upper parts in 4cy heuglini: the scapulars and mantle are grey, adult-like feathers. Some brown greater (especially in the outer greater coverts) or lesser coverts (in the carpal edge) may be present.

Tail: white. We did not come across enough birds to get in-depth insight in the variation of the tail pattern in sub-adult heuglini.-

Legs flesh-coloured, pink or pale yellow.