Bluethroats Luscinia svecica namnetum offset landscape constraints by expanding their home range

The highly fragmented landscape structures of coastal salinas are known to result in decreased terrestrial bird abundance, species richness and diversity but to promote original assemblages dominated by specialist species, such as the Bluethroat Luscinia svecica namnetum. This species is mainly found at the core of these salinas, where the landscape characteristics are a priori the most hostile for terrestrial birds. The aim of this study was to test whether individuals of a specialized species like the Bluethroat may offset such landscape constraints by expanding their home ranges. We therefore radio-tracked 21 males in 2013 and 2014 in the salinas of the Marais du Mes (Parc Naturel Régional de Brière, Western France). The data of the 18 best-monitored males were used to carry out a hierarchical partitioning of variance to test the relative influence of landscape characteristics, individual characteristics and distance to other males on their home-range sizes. We found that landscape characteristics were the factors that best explained home range sizes. Home-range sizes were significantly smaller in diversified landscapes composed of tidal creeks and salt-marsh patches and tended to be larger in landscapes dominated by the aquatic matrix consisting of water ponds. The results of this study demonstrate that although a few bird species are able to
select a priori hostile landscapes, they can offset such constraints by expanding their home-range size.