Use of passive-infra-red-triggered trail cameras to study timing of breeding and habitat use of Corncrakes Crex crex in Scotland

Capsule: An assessment of the utility of deploying trail cameras to describe the timing of breeding and habitat selection by Corncrakes. Aims: To estimate the hatching dates of broods of Corncrake chicks and the timing of occurrence of juvenile birds and compare the intensity of use of two distinct habitats. Methods: Trail cameras deployed in and adjacent to agricultural grassland managed for silage production and livestock grazing captured images of Corncrakes. Young of the year were aged using plumage characteristics. Hatching dates and the timing of breeding were compared with expectations from a previous simulation modelling study based on radio-tracking and observations of broods during mowing. Intensity of use (calculated as the number of days on which images were obtained per day of camera deployment) was compared between previously mowed initially short habitat and taller early cover habitat. Results: Timing of breeding indicated by the camera study was broadly similar to that expected from previous studies using other methods. The intensity of use of early cover habitat by young of the year remained higher throughout summer than that of initially short habitat, even though the latter increased in height substantially during the breeding season. Conclusion: Trail cameras have considerable potential for studies of timing of breeding and habitat selection by Corncrakes, whose chicks and females are difficult to mark with tracking tags and whose secretive habits make searching for nests and broods and other direct visual monitoring methods impractical. This approach could be applied to other species with secretive habits. The design of camera surveys, including ours, would benefit from improved stratified sampling and optimisation of camera densities in different habitats. Preliminary results suggest that Corncrake conservation would benefit from increasing the proportion of land that is managed to produce tall early cover vegetation, rather than grassland mowed for silage.