Mating system flexibility in the Great Bustard: a comparative study

An analysis is made of the mating system in the Great Bustard (Otis tarda) by focusing on its flexibility. The study is based on a comparison of different populations in western Spain, and also of 2 successive years for the same population. The mean size of female groups was found to be related to harem defence, while the proportion of adult males present in the area and lower female group size appear to be associated with larger all-male groups and lekking behaviour. Changes in weather conditions, involving changes in the timing of mating, diet composition and social parameters, give rise to changes in mating strategies, thus leading to modifications in the mating systems observed.