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Arizaga J.,Aranzadi science Society | Mendiburu A.,Aranzadi science Society | Andueza M.,Aranzadi science Society | Andueza M.,University of Valencia | And 3 more authors.
Acta Ornithologica | Year: 2011

The Aquatic Warbler Acrocephalus paludicola is a globally threatened songbird and its decline is related to habitat loss. Accordingly, most studies dealing with the stopover ecology of this species have been chiefly focused on the habitat use and the availability of suitable habitats along its route of migration. In contrast, much less attention has been paid to other environmental causes potentially explaining the use of stopover sites. Our aim here was to investigate whether the Aquatic Warbler at an apparently suboptimal stopover site with small area of suitable habitats stops over only during adverse weather conditions. We used data obtained at a suboptimal (Jaizubia marshland, northern Iberia) and another optimal (Villefranque, southwestern France) stopover sites during the autumn migration over four seasons (2007-2010). The Aquatic Warbler tended to stop over at Jaizubia in days with rain, a fact that was not so evident at Villefranque, supporting the hypothesis that they used the suboptimal site only, or mostly, when adverse weather conditions forced them to land. In contrast, the optimal habitat was used independently of weather conditions. To properly identify key stopover localities for the Aquatic Warbler, we should consider the potential influence of adverse weather in occurrence of individuals, especially in small areas without preferred habitat.


Arizaga J.,Aranzadl Science Society | Andueza M.,Aranzadl Science Society | Azkona A.,Aranzadl Science Society | Dugue H.,Association pour la Connaissance et la Recherche Ornithologique Loire et Atlantique ACROLA | And 8 more authors.
Alauda | Year: 2014

The Aquatic Warbler Acrocephalus paludicola is one of the most threatened passerines in the world and the only under risk of extinction in mainland Europe. The goal of this work is to determine the relevance of wetlands of the Bay of Biscay for the Aquatic Warbler, during the autumn migration period. To test this we used ringing data on migrants caught at reedbeds Phragmites spp. in six sites using a common sampling protocol, during the autumn passage of 2011. The standardized number of captures tended to decrease from North to South in France (from 1.8 to 0.3 captures/100 m of mist nets/d), and it was very low in northern Iberia (< 0.2 captures/1 00 m of mist nets/d). The percentage of captures of Aquatic Warbler in relation to all Acrocephalus was 1.5% but it differed between stations, with higher-than-expected values at two wetlands from southwestern France (4.2% and 3.7%). The proportion of first-year birds and the mean fuel load tended to decrease from North to South in France (analyses not done for Iberia due to the small sample sizes). All this is discussed under the point of view of the identification of target stopover places for the Aquatic Warbler and its strategy of migration in the Bay of Biscay, considering that a single sampling year was here used.

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