Importance of Intertidal Wetlands for the French Coastal Endemic Bluethroat Cyanecula svecica namnetum and Conservation Implications in the Context of Global Changes

Abstract

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.

Stopover ecology of autumn-migrating Bluethroats (Luscinia svecica) in a highly anthropogenic river basin

“…Much less known was the preference of migrating Bluethroats for corn crops, although one study had detected this species in this crop type during migration (Gottschalk & Cover 2016) and some populations of Bluethroats seem to thrive and even breed successfully in some agricultural fields, such as oilseed rape crops (Cornulier et al 1997;Berndt andHölzl 2012, Chiron 2017). We did not find the preference of Bluethroats for tidal mudflats or low-halophytic vegetation described in other studies (Arizaga et al 2013;Godet et al 2015;Musseau et al 2017), but the representation of these habitats in Barthes de la Nive is relatively limited, which could explain this lack of use. Our results showed that home-range size is smaller when birds occupied reedbeds (for overall home ranges) and corn crops (for daily home ranges).…”

“…Migrating Bluethroats in Barthes de la Nive strongly selected reedbeds (pure and mixed) and other hydrophilic natural grasslands, which concurs with the favourite habitat that Arizaga et al (2013) and Musseau et al (2017) found for migrating and moulting conspecifics, respectively. Much less known was the preference of migrating Bluethroats for corn crops, although one study had detected this species in this crop type during migration (Gottschalk & Cover 2016) and some populations of Bluethroats seem to thrive and even breed successfully in some agricultural fields, such as oilseed rape crops (Cornulier et al 1997;Berndt andHölzl 2012, Chiron 2017).…”

“…Additionally, overall home ranges are nearly twice to three times larger in Barthes de la Nive than in Txingudi (Arizaga et al 2013). Musseau et al (2017) also found home ranges of similar size to Arizaga et al (2013) in moulting Bluethroats.). These contrasting differences between Txingudi and Barthes de la Nive are very likely mediated by the strong differences in the degree of urbanization and habitat composition that seem to have profound consequences in the stopover behaviour of Bluethroats between two relatively close locations.…”

“…This highlights the relevance that the surrounding matrix might have even for a wetland specialist as the Aquatic warbler. Conversely, Bluethroats are migratory birds that can use a large range of habitats, mainly reedbeds and marshlands (Arizaga et al 2006;Musseau et al 2017), but also bushlands, woodland and farming habitats (Cramp 1988;Cornulier et al 1997;Chiron, 2017, Berndt andHölzl 2012), making it an interesting model to study its stopover ecology and habitat selection during migration. Arizaga et al (2011) radiotracked 20 autumn-migrating Bluethroats in Txingudi (North Spain), a wetland located less than 30km away from Barthes de la Nive.…”

Mapping the Rapid Decline of the Intertidal Wetlands of China Over the Past Half Century Based on Remote Sensing

“…Apart from hydrological disasters such as floods, seawater backwash, storm surge, etc., which have been discussed extensively in previous research, intertidal wetland loss will also result in tremendous environmental, ecological, and biological impacts due to the destruction of the habitat (Musseau et al, 2017;Spivak et al, 2019). A recent forecast estimates a net loss of intertidal wetland coverage ranging from 28% to 57% by the year 2100 (McLachlan, 2018).…”