Slaty-backed Gull Larus schistisagus
           Sakawagawa-river Odawara Kanagawa Japan, January 3rd 2002
a
  adult winter 
a
 adult winter
 adult or sub-adult winter 
 sub-adult
 probable 4th-winter
 3rd-winter
 a
 sub-adult
 4th-winter?
 adult or sub-adult winter
 adult or sub-adult winter
 3rd-winter
a