Heuglini 2cy, March 2 2001, Bahrain: Ashkar harbour. 

Another very powerful and dominant individual with a warm brown tone on the juvenile coverts. The bill is pale pink at the base with a dark tip. Here, the under wing is pale and the inner primaries are medium pale again; so, not really creating a pale window. The inner tail feathers are missing, the others appear all dark. Like in ordinary 2cy heuglini, extensive streaking runs all the way down the flank and on the breast, streaking almost creates a band. Note the very vicious facial expression in all the images. The tertials are still juvenile, with a black centre and the new coverts show a grey base with a faint sub-terminal band, creating a delicate anchor pattern. Note the extensive dark centres of the juvenile outermost greater coverts.

In Bahrain, such large birds are either cachinnans or heuglini. Cachinnans, being a southern breeder from the steppe belt, normally doesn't show such fresh looking juvenile feathers (note the greater coverts) and cachinnans normally doesn't show active post-juvenile moult in February. Moreover, most cachinnans have finished their post-juvenile moult by early November as 1cy birds. Hence, active post-juvenile moult in February in 2cy birds is a strong indicator for nortern breeders from the tundra region, i.e. heuglini and fuscus in Bahrain.

By July, when some of these birds return to N Europe, the wing-coverts will appear worn and they show just a simple arrow-pattern.