Metabarcoding insights into the diet and trophic diversity of six declining farmland birds

Knowledge of feeding ecology of declining species, such as farmland birds, is essential to address their conservation requirements, especially when their habitats are suffering important reductions of trophic resources. In this study, we apply a metabarcoding approach to describe the diet composition of six of the most significant farmland birds inhabiting European cereal pseudo-steppes: little bustard, great bustard, pin-tailed sandgrouse, black-bellied sandgrouse, red-legged partridge, and common quail. We further studied seasonal diet variations (autumn to spring) in all species but the common quail, whose diet was studied during spring and summer. We show that study species´ diets mostly consisted of plants, although in the case of little bustard and great bustard arthropods are also highly relevant. Among arthropods, we found high proportions of thrips, arachnids, and springtails, which were previously unreported in their diet, and some taxa that could be used as antiparasitic food. Moreover, we report that little bustard’s diet is the least rich of that of all studied species, and that diet of all these species is less diverse in winter than in autumn and spring. Diet composition of these declining species supports the importance of natural and semi-natural vegetation and landscape mosaics that can provide a wide variety of arthropods, plants, and seeds all year-round.
This paper contributes to the REGRESSEDS project (CGL2016-75278-R funded by MINECO, Spain). This study is also a contribution to project Sistemática, Biogeografía, Ecología del comportamiento y Evolución (IT1163-19) funded by Basque Country Government. Additional funds for this study were provided by the projects 201630E096 funded by CSIC (recipient BA) and AGROPERDIZ (SBPLY/17/180501/ 000245) funded by the “Junta de Comunidades de Castilla-La Mancha” and “Fondo Europeo de Desarrollo Regional” (recipient FM & BA). Xabier Cabodevilla was supported by a Ph.D. grant, financed by the Basque Country Government (grant no. PRE_2018_2_0273).