EERDE K VAN (1998) Autumn migration of Aquatic Warbler Acrocephalus paludicola at the Makkumer Zuidwaard in 1986-96. LIMOSA 71 (4): 149-152.

The Makkumer Zuidwaard, on the Frisian coast of Lake IIsselmeer, is one of the few sites in The Netherlands where Aquatic Warblers regularly occur during autumn migration. In 123 trapping days in the period 1986-96 a total of71 birds (of which only one adult) were caught in mist nets and ringed. Aquatic Warblers were caught between 25 July and 18 September, but most often during the first half of August. A smaller peak in early September was probably caused by arrival of young from second broods. Juveniles were on average heavier and showed more visible subcutaneous fat (11.8 g, median fat score 3) than juvenile Sedge Warblers A. schoenobaenus caught at the same site (10.9 g, fat score 1). Two birds were recovered so far, one from Finistere, France, and one from Neubrandenburg, Germany. The question why Aquatic Warblers are so often recorded at Makkum in comparison to other Dutch reedland sites, some of which have similar vegetation and are also regularly visited by bird ringers, is discussed. It is suggested that there is a narrow migratory corridor via the Frisian IIsselmeer coast towards the SW-Netherlands and NWBelgium, where comparatively large numbers are recorded as well. Aquatic and Sedge Warblers seem to exhibit different migration strategies.

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