Predicting short-term extinction risk for the declining Little Bustard ( Tetrax tetrax) in intensive agricultural habitats

Abstract

Populations of Little Bustard ( Tetrax tetrax) have shown pronounced declines in European farmland landscapes over the last 25 years due to the intensification of agricultural practices. In France, the number of breeding males in agricultural habitats has declined by 92% since 1980 as a result of decreases in insect abundance and nest destruction during harvesting. We formulate an age- and sex-structured stochastic model for the remaining Little Bustard population in SW France that has been studied since 1997 and, using actual values of demographic rates, we estimate its extinction risk over a time period of 30 years to be of 0.45. At the level of local populations, the extinction risk ranged between 0.66 and 0.90, largely depending on the initial population size and local fecundity of each population. A comprehensive sensitivity analysis evaluated the influence of uncertain demographic rates and of aspects of the spatial dynamics (sex and age dispersing individuals, sex-biased dispersal and different dispersal rates) on the predicted extinction risks and showed that our model was robust to changes of a wide range of combinations assessed. Given the severity of the current decline, and the spatial issues raised by our analysis, implications of our findings for the conservation of this endangered species are suggested.