Status and extinction probabilities of great bustard (Otis tarda) leks in Andalucia, southern Spain

Great bustards (Otis tarda) commonly occur in isolated populations consisti ng of only a few tens of individuals. Knowing where these are, and understa nding the factors affecting their persistence, is necessary to save this de clining species. A census (Spring 1999) was therefore made of possible grea t bustard lek sites in Andalucia, southern Spain. Forty-six males and 79 fe males were observed and a total of 180 conservatively estimated for the are as we visited. These were distributed among five, possibly six, leks, but m ost (66-72%) were recorded at only two localities. Through interviews with local people we established that at least two, possibly three, leks had bec ome extinct within the last two decades, and also learned of another lek of 50-70 birds in the north of the region. The precarious status of the four largest visited leks was demonstrated through computer simulation (VORTEX). This showed that under status quo conditions their likelihood of extinctio n within 100 years is 85-99%. Further simulations demonstrated the disastro us consequences of poaching with extinction probabilities of 95% reached in 8-70 years. However when a hypothetical management scheme was modelled the results were encouraging. In these simulations the number of chicks per fe male per year was increased from 0.14 to 0.18 and annual mortality of femal es was reduced from 7.5 to 5%. This resulted in extinction probabilities of only 20% within 100 years at the larger leks. Simple, practical conservati on actions to enhance annual recruitment and increase female survival are s uggested.