Feeding of the Black-necked Swan Cygnus melanocoryphus (Birds: Anatidae) in a marine wetland of Chiloe, southern Chile

Abstract

Considering Cygnus melanocoryphus as a generalist herbivore that feeds on algae and seagrass more abundant in wetlands, suggests the existence of unknown interactions between this waterfowl and the seaweed farmers in Southern Chile. Therefore the aim of this work was study the feeding of C. melanocoryphus in a marine wetland of southern Chile, where traditionally it has made the cultivation of algae Gracillaria chilensis. This work was conducted during the winter of 2011 in the marine wetland of Caulin bay (41°49’S; 73°38’W), in the Island of Chiloé, Southern Chile. C. melanocoryphus spent most of their time feeding, observing in this bird a behavior of selective herbivory food towards preferential but not exclusive consumption of the seaweed Ulva taeniata. The tidal cycle affected the spatial distribution of C. melanocoryphus; during times of low tide these were concentrated in the intertidal zone feeding on the fronds of U. taeniata retained or settled in the farming systems of G. chilensis. While during high tide periods C. melanocoryphus entered to the supratidal zone by following the fronds of U. taeniata in the drift of the currents, watching they feed on the dominant seagrass (Distichlis spicata and Selliera radicans) in the estuarine zone. The knowledge obtained allows argue the hypothesis of an environmental service provided by C. melanocoryphus for the "algueros" of the wetland, by removing of the seaweed U. taeniata from culture systems of G. chilensis freeing his competition over substrate and light to grow.