Variation in diet composition of wintering waterfowlamong Greek wetlands

Karmiris I., Kazantzidis S., Papachristou T. G.

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The aim of this study was to determine the diet composition of wintering waterfowl, and assess its variation among Greek wetlands. Digestive tracts (oesophagus, proventriculus and gizzards) of Gadwall Anas strepera, Eurasian Wigeon Anas penelope, Eurasian Teal Anas crecca, Mallard Anas platyrhynchos, Northern Shoveler Anas clypeata, Northern Pintail Anas acuta and Common Coot Fulica atra were collected in four Greek wetlands (Evros Delta, Lake Vistonida, Aliakmon-Axios Delta and Messolonghi Lagoon), during two wintering periods from October 2004 to March 2006. Diet composition was evaluated using the percentage of occurrence and the aggregated percent dry weight methods. Gadwall and Wigeon were primarily herbivorous (both more than 95% dry weight), Teal and Mallard mostly relied upon seeds for food (60-75% dry weight), whereas Shoveler, Pintail and Coot consumed elevated quantities of invertebrates (27.4%, 16.8%, and 31.2% dry weight respectively). Scirpus consumption by Teal and Mallard was lower in Messolonghi Lagoon than in the other wetlands. Conversely, increased quantities of Ruppia spp. and invertebrates were recorded in waterfowl diets (except Teal) in Messolonghi Lagoon. These fndings may be attributed to the variation in food availability among study areas, thus management plans should be focused both upon the targeted bird species and the particular wetland separately. In general, since studied species exhibit considerably forage plasticity, providing increased habitat heterogeneity seems to be the best management approach for wintering waterfowl in Greece, at least under their dietary needs’ aspect.