Slaty-backed Gull (schistisagus) / オオセグロカモメ / 큰재갈매기

(last update: December 2015)

Slaty-backed Gull (schistisagus) 3rd cycle / 3CY December

3rd generation flight feathers. In general these are adult-like birds, with obvious immature markings. Ageing can be difficult at this age, especially between 3CY and 4CY birds. Immature birds with extensive black in the tail and extensive brown wing-covert patches should normally also be in 3CY. However, advanced 3CY and retarded 4CY birds are extremely similar, and such birds are probably best labelled "sub-adult".