Influence of habitat quality and diversity on two populations of Eurasian curlew (Numenius arquata) with contrasting dynamics in Western France

Like most shorebirds in Europe, breeding populations of Eurasian curlew (Numenius arquata) are suffering from habitat loss and degradation mainly caused by changes in agricultural practices. In Deux-Sèvres (France), the number of pairs has gradually declined since the early 2000s in the main, historical breeding site, while a new breeding site has appeared recently 80 kilometres further north with increasing number of pairs through the survey period. Many wheat fields and rare dry grasslands are found in the north, whereas the landscape in the south is mainly composed of tillage plots, hay meadows, and pastures. This study aims to highlight differences in food availability and quality between the two areas. Sample series of ground-dwelling and vegetation-dwelling invertebrates were carried out during three key stages of the species breeding cycle with pitfall traps and sweep nets. Dry grasslands in the north were found to be the most favourable habitat in terms of prey availability for adults and for chicks during the brood-rearing period. Moreover, hay meadows and pastures in the south seemed to be resource-abundant feeding habitats. Therefore, the habitats of the northern site seem to offer a greater abundance of invertebrates and thus a potentially larger food resource than the southern one. It follows that the northern site likely offers better breeding conditions, especially for the growth of chicks. An increase in the area of dry grasslands in the north and the establishment of adapted agricultural management in the south would be favourable for the conservation of local curlew populations.