Fall Migration of the Slaty-backed Gull Larus schistisagus Stejneger, 1884 Based on the Results of the First GPS-GSM Tracking Study

This paper presents the first results of tracking the fall migration of the adult Slaty-backed Gull (Larus schistisagus) using GPS-GSM loggers from a nesting colony in the northern Sea of Okhotsk (Taui Bay) to the wintering region (Hokkaido Island). The migration distance (2600–4300 km) classifies the Okhotsk Sea population as “long-distance migrants.” Similar to other large white-headed gulls, Slaty-backed Gulls employ a “fly-and-forage” migration strategy during fall, with significant variations in routes and individual travel tactics, utilizing individual experience in choosing the stopover sites. The gulls preferred coastal migratory routes and exhibited flexible travel behavior. Birds used both overland and open-sea crossings to shorten their path and were active in the daylight and at twilight. Overall, fall migration of Slaty-backed Gulls is characterized by a low migration speed; close trophic relationship with Far Eastern (Pacific) salmon; and the use of anthropogenic food sources, while following fishing vessels and utilizing fish-handling waste and food scraps in settlements.