Status and recent trends of the great bustard (Otis tarda) population in the Iberian peninsula

摘要

We present an updated estimate of the great bustard population in the Iberian peninsula. The sum of the most recent counts was 20,243, and the estimated total, 24,490 birds. During the last two decades bustards increased at five intensive study areas, remained stable at two, and declined or became extinct at eight. These population changes were determined by both variations in breeding success at each area and migration of birds between areas. Our results suggest that the population is probably concentrating at high quality areas, and disappearing from poor quality ones. We also identified 29 areas where bustards have become extinct during the last four decades, mostly due to hunting and agricultural transformations. In conclusion, although the population is apparently not decreasing at present, the concentration trend described could lead to a higher species' vulnerability, a loss of genetic diversity, and a further isolation of marginal groups. Strict conservation measures should thus be directed at preventing the decrease of the number of extant leks.