High-resolution tracking data highlight the importance of fallow land during a seasonal habitat bottleneck for a steppe-land specialist

Farmland ecosystems are seasonally dynamic habitats shaped by meteorological fluctuations and anthropogenic land-use changes. Farmland birds may be seasonally constrained with limited foraging and breeding resources (so-called “resource bottlenecks”), especially when there is a loss of natural and semi-natural habitats. During spring, the growth of cereal crops makes a large proportion of arable land unsuitable for specialist steppe birds with narrow vegetation structure requirements. We investigated the existence of a seasonal bottleneck of suitable habitats for steppe birds using the endangered Pin-tailed sandgrouse (Pterocles alchata) as a model species. We used for first time lightweight GPS tags to study habitat selection and movement patterns throughout the cereal crop cycle during three years in north-eastern Spain. We also evaluated if conservation measures promoting suitable vegetation structures for steppe birds (Targeted Fallow Management, TFM) influenced habitat selection. Sandgrouse avoided cereal crops when cereal vegetation was high, resulting in a 30% reduction of suitable habitat area at the start of the breeding season. This proved the existence of a spring habitat bottleneck when sandgrouse only selected open natural habitats and fallows. Sandgrouse similarly selected TFM and conventionally managed fallows during and after the bottleneck, possibly because of their similar vegetation structure and the scarcity of alternative suitable habitats. Halting the ongoing loss of fallow land is paramount for the conservation of steppe birds like sandgrouse because they constitute a key refuge to buffer the impacts of seasonal habitat bottlenecks.

Infrastructures from the Generalitat de Catalunya funded this project. RT was supported by a Juan de la Cierva-Formación [FJCI-2016–28540] and the project "CLU-2019–01 - iuFOR Institute Unit of Excellence" of the University of Valladolid and co-financed by the European Regional Development Fund (ERDF "Europe drives our growth") [CP21/75]. AS-P was partially funded by the Forest Science and Technology Center of Catalonia.

Peer reviewed