Male corncrakesCrex crexproduce characteristic repetitive calls composed of two elements. Duration of each element, and the interval between elements and between calls, were measured for a single bird on three nights and for five birds on a single night. Element durations were similar on all three nights but interval durations differed between nights. Element durations differed between birds but some pairs of birds could not be separated using measures of element duration. Call elements are made up of pulses and the number of pulses differs between elements of a call.