Great Bustard (Otis tarda) nest locations in relation to leks

Abstract

We investigated the spatial arrangement of Great Bustard Otis tarda nests relative to leks in 55 females captured at four lek sites and radio-tracked through 1–6 years in a protected area in central Spain. Although females showed a tendency to nest close to the lek centers where they were observed during the mating season (29% did it at <2 km), lek-to-nest distances ranged between 0.22 and 53.82 km. This resulted in most nest-sites (64%) being outside the lek areas where the female had mated, often closer to nearby leks, and sometimes far from any lek, in areas used only for nesting, outside the protected area (25%). The distribution of nest-to-nearest-lek distances did not differ from that of randomly distributed control sites, indicating that nest-sites were not aggregated, but dispersed over the whole suitable habitat within a large area around leks. Females with and without hatching success did not differ in their mean lek-to-nest distance. These results suggest that females used the whole suitable habitat available for nesting, and did not base nest-site selection on factors related to density-dependent disturbances or predation risks at leks (lek avoidance hypothesis). In this and other lekking birds, managers have often restricted conservation efforts to lek areas, under the wrong assumption that these would include most nest-sites. If a much larger region including most nesting habitat is not protected, Great Bustards in our study population might eventually be forced to nest at higher densities within the protected area, with a consequent density-dependent reduction in the mean breeding success of the population.