Summary
A total of 579 Sedge Warblers (Acrocephalus schoenobaenus) on their autumn migration have been ringed in Val Campotto in 1986. Adults showed a more concentrated passage than juveniles. Adults were in a more advanced stage of fat accumulation with respect to juveniles; in the former, body mass values were lower than those reported for other sites at higher latitudes. The preferred direction for juvenile birds tested in August and September/October was south, so fitting with the suggestions of other authors. The same direction was observed in fat and lean birds, although the latter were less homogeneous in their directional choices. Most captures took place within few hours after dawn. The absence of Sedge Warblers later in the day, and the morning migratory restlessness suggest that this area with very poor food resources is soon abandoned by the birds.
Zusammenfassung
Im Val Campotto, Norditalien, wurden auf dem Wegzug 579 Schilfrohrsänger gefangen. Die Altvögel zogen konzentrierter durch als die Jungvögel. Sie waren auch in einem fortgeschritteneren Stand der Fettanlagerung als juv. Gleichwohl hatten die ad. geringere Körpermassen als an anderen Fangplätzen höherer Breiten. Die Vorzugsrichtung der juv. war S in Übereinstimmung mit Erwartungen aus Literaturangaben. Fette und magere Vögel zeigten gleiche Vorzugsrichtung, wenn auch letztere größere Streuung in der Richtungswahl aufwiesen. Die meisten Vögel wurden am frühen Morgen gefangen. Die morgendliche Zugunruhe und das Fehlen der Schilfrohrsänger in späteren Tagesstunden lassen vermuten, daß das Untersuchungsgebiet nur geringes Nahrungsangebot aufweist und rasch verlassen wird.
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Spina, F., Bezzi, E.M. Autumn migration and orientation of the Sedge Warbler (Acrocephalus schoenobaenus) in northern Italy. J Ornithol 131, 429–438 (1990). https://doi.org/10.1007/BF01639819
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DOI: https://doi.org/10.1007/BF01639819