Migration and wintering locations in the barred warbler Sylvia nisoria
Abstract: Technological advancements in the past few decades have been pushing the research field of animal migration forward rapidly. In this study light-level geolocators were used to track Swedish barred warblers Sylvia nisoria, a long-distance migrant wintering in equatorial East Africa. We obtained data on autumn migration events and on wintering sites. Ringing data from populations in Northern Europe were added to support and refine the patterns found. The birds departed from breeding grounds during the first half of August and migrated towards Southeast passing through the Balkan Peninsula and the Levant (Syria, Lebanon, Jordan, and Israel), seemingly avoiding the Mediterranean. In September they arrived in the Sahel region for a long stop-over, previously undescribed. The stop-over lasted until November when they proceeded to the final wintering site just north of the equator where they then remained during winter. Migration speed was consistent with what theory predicts and the timing of migration could be described and compared to species migrating along similar routes. The arrival and departure to Sahel coincide with the expected based on the seasonal variation in precipitation and food abundance. The study also include observations on the rare split wing moult strategy conducted by the barred warbler and a theory that explains how time and food availability is restricting time available for moulting in this species and some parallel cases, driving the moult to be split into two different occasions.
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