Wild birds, in particular waterfowl, are common reservoirs of low pathogenic avian influenza viruses, and infected individuals could spread the viruses during migrations. We used satellite telemetry to track the spring migration of the mallard ducks ( Anas platyrhynchos ) that winter in Japan. We studied their migration routes, distribution of stopover and breeding sites, and timing of migration movements. We tracked 23 mallards from four different wintering sites. Nine of the 23 mallards reached presumable breeding sites, where migration terminated. The migration routes of the birds greatly differed not only among the wintering sites but also within the same wintering site, although the general feature of the routes was shared among birds within the same wintering site. The mallards used several stopover sites, and they typically stayed for a long period (about one to four weeks) at a site between migration intervals of two to three days. Stopover sites were located in northeast Japan, the eastern coastline of South Korea and North Korea, and the interior of Far Eastern Russia. Mallards from three different wintering sites used a stopover area near the middle part of the Ussuri river in Russia. The terminal sites, which were presumably also breeding sites, were distributed widely over northeast Asia and Far Eastern Russia. These results suggest that mallards that winter in Japan originate from breeding areas widely distributed across eastern Asia. Mallards could potentially transmit avian influenza viruses between Japan and a broad region of northeastern Asia.

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We describe the detoured migration route of the Oriental honey-buzzard Pernis ptilorhyncus, showing differences between autumn and spring migration, using data from 10 adult individuals marked with satellite transmitters. In autumn, the migration routes were very similar from Japan to the south end of the Malay Peninsula. The wintering sites were distributed within the Philippines, Borneo and the Malay Archipelago. During autumn, migration of the birds had few long-term stopover sites, instead, sometimes decidedly slowing their migration rate while proceeding in a consistent direction. During spring migration, the honey-buzzards penetrated into southern China, moving north to the base of the Korean Peninsula. The birds then went south through the Korean Peninsula to reach Japan. Before travelling to China, all spring migrants stopped for several weeks in south-east Asia. The slow rate of travel in the autumn suggests that migrants were foraging and replenishing their energy reserves. Instead of a migration strategy that uses only a few long-term stopover sites, honey-buzzards may adopt a strategy based on a number of short-term stay sites.

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