January 2014
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26 Reads
Alauda
The Brière marshland is a Natura 2000 area where data on the postnuptial passage of this species were collected in order to improve the ecological knowledge on the rare and threatened Aquatic Warbler in Europe. Data deal with the carrying capacity of the Grande Brière - Donges and Brivet marshlands. Ringing of birds was carried out in August 2009, 2010 and 2011 at three sites which constitute the Natural Reserve of Brière marshland. 252 individuals were ringed during the three years, the Aquatic Warbler representing 3.6% of the 6,855 captured birds. At the three sites, 4.42 individuals of Aquatic Warbler were captured per day and per 100m of mist-nets. In 2011 the southern site totalized 70% of the captures with 9.95 individuals per day and per 100m of mist-nets, one of the highest value ever obtained in France. The habitats of each ringing site and food resources have been studied. The entomological survey showed the occurrence of more than 6,000 arthropods distributed over 8 orders and largely dominated by dipteran flies. 207 droppings have been analyzed to compare the diet of three Acrocephalus species (Sedge, Aquatic and Reed Warblers). The droppings of Aquatic Warbler showed a strong dominance of dipteran flies and a high proportion of large-sized arthropods. These prey-items showed that the Aquatic Warblers do not only exploit reedbeds but also, and importantly, the borders between water areas, reedbeds and wet grassy areas. This study emphasizes the high ornithological value of the Brière and Brivet marshlands and their associated reed- and open areas for the postnuptial migration of the Aquatic Warbler.