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Résumé :
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Very few land bird species in the East Asian-Australasian Flyway regularly winter in Australia. One such species is the Pacific Swift Apus pacificus. Using light-level geolocators, we tracked the almost 10,000 km long journey of three individuals between Sakhalin Island (Russia) and Australia. Migrating individuals avoided prolonged sea crossings; both during the southward and northward migrations they performed detours, moving from Sakhalin to the nearest Asian continent (Primorie, Russia), reaching northern Australia via Indochina and the Indonesian archipelago. Southward migration duration was on average 12 days longer than northward migration, although stopover duration did not differ between boreal fall and spring. However, during the northward migration, swifts stopped much closer to the Australian wintering grounds (in Indonesia and around Vietnam) than during the southward migration (Southern China and Vietnam). We suggest that migration to and from Australia is rather challenging for an insectivorous terrestrial bird, particularly during northward migration, requiring adjustment of timing to match contrasting meteorological patterns: the dry season in Northern Australia, the end of the wet season in Indonesia, and the start of the wet season in Indochina. Furthermore, swifts must cope with delayed phenological spring in Northeast Asia, possibly causing them to wait at Southeast Asian stopover sites before rapidly reaching Sakhalin breeding grounds in the early boreal summer.
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