VAN DER SPEK V, DE JONG A, VAN WINDEN E & ROSELAAR CS (2020) Has the autumn migration phenology of Aquatic Warbler Acrocephalus paludicola changed in the Netherlands?. LIMOSA 93 (3): 129-137.

Here we compare the past and present autumn migration of Aquatic Warbler, a scarce migrant and former breeding bird in the Netherlands. Lighthouse and lightship victims collected in autumn between 1887 and 1971 (but mainly before 1958), as preserved at the National Institute for Biodiversity Naturalis, yielded insight in past migration patterns. Based on 205 records, migration showed two clear peaks: early August and mid-September. Median migration date was 6 September (Fig. 2). There was only one July record, while there were 14 October records. Apparently, migration in October was not exceptional at that time. Recent records of Aquatic Warblers (field observations and captures, 1994-2013; N=676; Fig. 4) do not show a second peak in September. July records are increasingly common whereas October records (only 2) are rare. Median migration date was 10 August. The absence of a second peak and consequently one month earlier median migration date is notable. Notwithstanding the differences between the datasets, these observations suggests a shift in migration phenology of Aquatic Warblers in the Netherlands over time.

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