BioSphere Environnement

Mortagne-sur-Gironde, France

BioSphere Environnement

Mortagne-sur-Gironde, France
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Musseau R.,BioSphere Environnement | Beslic S.,BioSphere Environnement | Kerbiriou C.,CNRS Science Conservation Center
Ardeola | Year: 2017

Summary. Coastal specialised species have naturally restricted distribution areas and may be drastically affected by fragmentation or loss of their habitats due to ongoing changes, such as artificialisation, shoreline erosion, rising water levels or colonisation by invasive species. In this context we characterise the land occupation strategies of a Western Atlantic French coastal endemic bird: The Bluethroat Cyanecula svecica namnetum. Our study focuses on a key period of the life cycle of this species: The post-breeding moult. Capture and recapture sessions in intertidal habitats have allowed us to retrieve 26% of local breeders during their moulting period. The modeling of moult kinetics revealed that moult of flight feathers takes 37-50 days. A radio-tracking survey of moulting birds revealed exploitation by individuals of both the lowest and tallest vegetal formations of intertidal sites and exploitation of small home ranges (0.42-1.34 ha), typical of locations where trophic resources tend to be abundant and predictable. Analyses of droppings highlighted that Coleoptera, Aranea and marine crustaceans (Amphipoda) contributed most of the prey biomass consumed, amphipods being particularly selected by birds in active moult. Our results underline the importance of intertidal wetlands in terms of trophic opportunities to compensate for the energy costs of moult for the Bluethroat. Given the global changes already dramatically affecting coastal habitats, we emphasise that special attention should be given to the conservation of intertidal wetlands for marshland passerines of conservation concern such as the Bluethroat, and that restoration of adjacent coastal terrain is a promising development.

Jiguet F.,CNRS Science Conservation Center | Chiron F.,CNRS Science Conservation Center | Dehorter O.,CNRS Science Conservation Center | Dugue H.,Association ACROLA | And 9 more authors.
Acta Ornithologica | Year: 2011

The autumn world population of the endangered Aquatic Warbler Acrocephalus paludicola probably numbers between 23 000 and 69 000 individuals, including 5 000 to 44 000 first-year individuals, depending on variation in breeding success and post-fledging survival. After breeding, the species migrates as early as August along a westerly route along French coast to reach its African wintering grounds. In 2009, French ringers have carried out targeted mist-netting to enhance the capture of the species, using tape luring in suitable habitats. Overall, 874 different individuals were captured in France in that year. In 2010 similar ringing effort allowed the capture of 646 different individuals. From this ringing information, we propose a simple method to estimate the number of individuals which stopped in the country during the autumn migration, considering all birds or first-years only. Splitting the country in two parts (northern and southern), the method uses the total number of captures and the number of southern recaptures of birds first ringed in the north. Overall, we estimated that between 24 000 and 30 000 individuals most of them in their first calendar year stop in France each year during the fall migration. These estimates suggest that probably all first-year Aquatic Warblers migrate by this western flyway and stop in France to refuel, while adults may partly use a different flyway or may stop in France, but for shorter times or at fewer sites. The proposed figures highlight the importance of maintaining suitable refuelling habitats for the species all along coastal France.

Arizaga J.,Aranzadi science Society | Musseau R.,BioSphere Environnement | Musseau R.,British Petroleum | Laso M.,Aranzadi science Society | And 4 more authors.
Bird Study | Year: 2015

Capsule: The effects of playback use on number of captures, recaptures, fuel load, and age and sex ratios, and so potential bias in stopover studies in migrant Bluethroats was investigated. Playback promoted biases in the number of captures (although this was site-dependent) and fuel load. We strongly advise against the systematic use of playback to sample Bluethroats at constant effort sites or other type of ringing station, especially if studying fuel loads. © 2015 British Trust for Ornithology.

Musseau R.,BioSphere Environnement | Musseau R.,British Petroleum | Herrmann V.,BioSphere Environnement | Herrmann V.,British Petroleum | And 5 more authors.
Acta Ornithologica | Year: 2014

The Aquatic Warbler Acrocephalus paludicola is the only endangered songbird in continental Europe. This trans-Saharan migratory bird significantly transits along the French Atlantic coastline during post-breeding migration and the right bank of the Gironde estuary has been identified as an important stopover site. We studied the spatial occupancy strategies of stationing individuals during August of three successive years (2010-2012). We characterized habitat use by radio-tracking individuals revealing relatively small foraging ranges (6.6 ± 2.6 ha on average) with only 1 ha actually exploited (core area), and a relatively high habitat fragmentation rate. Capture-mark-recapture analyses assessed the average stopover duration of individuals and body-mass variations during their stopover. The estimated average stopover duration was 6.46 ± 0.46 days (95% confidence interval: 4.4-9.6). Lean birds tended to forage significantly more than stout birds: on average, they gain 2.81 ± 0.89% of their initial mass each day whereas stout birds only gain 0.12 ± 0.56%. Analyses of droppings characterized the local diet. We noticed that Aquatic Warbler preferentially used partially-flooded or flooded habitats with heterogeneous and rather low vegetation, such as bulrush beds or bulrush beds mixed with reed beds. Orthoptera, Araneae and Hymenoptera represented the largest contributions to the consumed biomass (64.7%, 13.4% and 8.9% respectively). The importance of the fuel deposition rate of lean birds reflects the importance of the estuary as a stopover site for the species. It means that the available resources allow birds to replenish and continue their migration route. However, the sustainability of the site's functionality is questioned because of the evolution of habitats (erosion, rise in water levels and changes in food web).

The Aquatic Warbler is the most threatened passerine in continental Europe (according IUCN scale). The species is a long-distance migrant which migrates along the French Atlantic coast in August during postnuptial passage. One of the major staging area is the right bank of the Gironde estuary in southwestern France. We started a research project in order to define the strategy of occupancy of staging individuals. Our study was carried out in August 2010, 2011 and 2012. A first question addressed was to study the habitats and their use by radio-tracked individuals. A second one was to ring and to control marked individuals in order to know how long they staged on the study area. Our results showed that the species used preferably partially flooded or liable to flooding areas where the vegetation cover was short (Scirpa, or mosaic of Scirpa and Phragmites). Individuals avoided dryer grassy habitats or homogeneous reedbeds. They used small home range of some 6.64 ha in size for a really exploited range of 1 ha. The mean duration of staging was of 6.64 days. Due to rapid environmental changes, the selected habitat by the species are highly threatened on the right bank of the Gironde estuary. In order to ensure the overall availability of suitable habitats for the species, we created shallow marshlands covered with short and heterogeneous vegetation which can be managed by extensive grazing.

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