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

(last update: December 2015)

Slaty-backed Gull (schistisagus) adult September

Birds in complete moult, with outer primaries still old and worn, inner and central primaries replaced. When P6 is growing, most birds start to shed the inner rectrices and outermost secondary S1.

Moult gaps in the wing-coverts will close, when the central greater coverts are replaced and the small feathers in the carpal edge are renewed (that will take place in October).

Secondaries and rectrices are in active moult; the secondaries are replaced by two moult waves. One moult wave from the body outwards, and another moult wave from S1 inwards. These two waves will meet at about S16-S17. Tail feathers are replaced centrifugal; the central feathers are dropped first and the outer rectrices last in line.