The bar-tailed godwit (Limosa lapponica) and the black-tailed godwit (Limosa limosa) are two migratory shorebird species that spend the winter on the French Atlantic coast, before to reach regions further north for breeding. These two species share great phylogenetic proximity, and great morphological similarities inherited from a common ancestor from which they recently diverged. In such “closely-related” species, although identical responses are generally observed facing the same environmental conditions, the existence of unique niche properties and specific ecological needs have already been described. It is the case in bar-tailed and black-tailed godwits, which share the same wintering areas, but have a distinct reproduction distribution, breeding respectively in northern Eurasia and Alaska, and from Iceland to eastern Siberia. In France, we mainly observe the subspecies L. lapponica lapponica for bar-tailed godwit, and the subspecies L. limosa islandica for black-tailed godwit, which are present throughout the wintering period (August-April). The subspecies L. lapponica taymyrensis and L. limosa limosa are only present during the migration periods (February-March and August-October). In winter, L. l. lapponica and L. l. islandica mainly use mudflat ecosystems, on which they depend for feeding, as well as marine and coastal marshes, for roosting. Thus, in the Pertuis Charentais (France), they use the same wintering sites and the same functional areas, but exhibit distinct food preferences with a diet dominated by polychaetes worms for the bar-tailed godwit, and bivalves (eg Macoma balthica) and seagrass rhizomes (Zostera noltei) for the black-tailed godwit. Beyond this knowledge, this thesis aims to describe and compare the winter survival strategies of these two species, and especially their spatio-temporal use of habitats. The recent miniaturization of GPS tracking loggers has enabled us to equip individuals of both species to access to their daily and seasonal movements. Such an approach can significantly help to improve our knowledge on the biology of these birds, their dependence on coastal habitats and their link with protected areas / nature reserves. More specifically, we aim to explore the resources selection (prey and habitats) of the two godwit species, in relation to the use of rare roost sites mainly located in nature reserves. Precisely identify birds feeding areas, using GPS position data, allows sampling of potential benthic macrofauna prey, in order to estimate the energy quality of feeding patches and to describe available habitats. In addition, the analysis of bird’s activity on a fine spatial and temporal scale also allows exploring their adaptation to the nycthemeral periodicities, crossed with the use of protected and unprotected areas. Finally, since these birds exhibit a strong sexual dimorphism, it appears interesting to explore the existence of sexual segregation in terms of winter survival strategy. More generally, it is possible to investigate the differences between individuals, or their interactions during feeding in order to test affinities between birds in a gregarious species such as the black-tailed godwit. This work thus provides new key knowledge on the wintering survival strategies of the bar-tailed and the black-tailed godwits, and particularly on their use, in space and time, of different habitats. The results obtained underline both intraspecific and interspecific differences may exist in these two very similar species, which should be considered in future management and conservation measures.