Energy crops as a new bird habitat: utilization of oilseed rape fields by the rare Bluethroat (Luscinia svecica)

As part of the expanding cultivation of renewable primary products, oilseed rape has become a prominent part of the agricultural landscape of many European countries. However, the ecological impacts of increasing cultivation of oilseed rape have received little attention so far. In this study, we provide the first systematic investigation of the suitability of oilseed rape as a habitat for the Bluethroat (Luscinia svecica cyanecula), an endangered and highly specialized bird species. We conducted territorial mapping and a habitat analysis, revealing the distinct habitat requirements of L. s. cyanecula in oilseed rape fields over three breeding seasons. The soil type was identified as the crucial factor for habitat occupancy. It acts as a surrogate for soil moisture and this in turn decisively influences food availability. Ditches can further improve habitat quality, whereas reed is not a necessary structure, although it is a regular feature in the primary habitat of the Bluethroat. Occupied oilseed rape stands were structurally different from the semi-natural reed habitat, but provided similar essential habitat requirements, such as shelter from predation and moist, bare soil. Our results clearly demonstrate the utilization of oilseed rape by a rare and threatened wetland bird species and suggest that this crop may act as a secondary habitat.