Biologia riproduttivadella cannaiola Acrocephalus scirpaceus in una zona umida dell’Italia Centrale

Quaglierini A.

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Breeding biology of reed warbler Acrocephalus scirpaceus in Central Italy. During twelve years (1999-2003), a study was carried out on the population of reed warbler Acrocephalus scirpaceus nesting in the Lake of Massaciuccoli, a large marsh in Central Italy. Data about location of nest and main reproductive parameters were collected. Reed warblers locate nests in pure reedbeds, upon young or two-year old stems. Nests are fastened to 3.5 stems on average, 91 cm above water surface and 32 cm far from open waters. Below nests, water is 15-cm deep on average, and reed density is 830 stems/m2. Nests are fixed to stems 231-cm high and 0.41-cm large. The complete clutch averages 3.5 eggs, a value lower than those reported in literature. Double brooding is a common feature, with first broods layed between May 4th and June 21th, and the second ones occurring between June 13th and August 8th. Hatching rate was 76.8%; and 82.8% of nestlings fledged successfully (1.95 fledged youngs per nest) for an overall reproductive output of 63.6%. No nestlings have been raised in 23.3% of checked nests. Although territories of the reed warbler are 440- m2 wide on average, the estimated total density in reed beds was 261 pairs/km2; thus a large part of suitable habitat for reproduction was not used. The breeding population is not decreasing, despite the general decay of the environment, because, contrary to great reed warblers, reed warblers are able to use also ecotones and intermediate-aged reed beds.