Heuglini adult, August 09 2002, Tampere, Finland (61.33N 24.59E).

Features suggesting heuglini in these pictures are upper-parts grey-tone. Birds obvious paler than fuscus. Facial expression: slender bill with well-defined gonydeal angle. General structure suggest female: pot-bellied bird, rounded head, different from the slender and 'elongated' look of fuscus.
Large mirror on P10, on both webs. Red spot doesn't extend to upper mandible, well in line with adult heuglini. P1 new, P2 growing, P3 missing, P4-P10 old, all rectrices and secondaries old as well.

General structure, especially head-shape and stubby bill with obvious gonys angle, not very reminiscent of cachinnans, which is often a good clue for heuglini. This kind of individuals at Tampere may also represent the paler end of fuscus (so not heuglini), or, considering the pot-bellied, short winged appearance, one may also argue this is the intermedius influence in core fuscus breeding area. Interestingly, in recent years, some ringed pullus within core fuscus area, turned out to be rather pale grey (near)adults.