Assessing the potential range expansion of the exotic monk parakeet in Spain

In this study we determine favourable areas for the monk parakeet, Myiopsitta monachus, in peninsular Spain to account for its current distribution and predict its future course according to its potential range. We applied a favourability function based on generalized linear models using the presence/absence of breeding colonies of the species and the values of a set of variables on the 5167 UTM 10 x 10 km squares comprising the study area. We calculated the factor of distribution change in presences predicted by the model, and grouped the variables into explanatory factors performing a variation partitioning to assess the explanatory power of each factor. Our model included six predictors to explain the presence and absence of the species. These predictors were grouped into three factors: human activity, climate, and topography. Purely human influences accounted for 63.8% of the variation of the final model, while topographical variables explained 15.2% and climate only 5.7%. We obtained a high distribution change factor in which the presences of the species were predicted to increase between two- and sevenfold. Taking into account highly favourable squares, we conclude that the species is still absent in more than 72% of potential settlement areas, and thus we expect a continuous increase in the distribution of the species. Human activity is the main force moulding the distribution of the species, and lies behind its fast expansion, which is not only active, but is also passive via releases and escapes. We identified the areas of likely future expansion of the exotic monk parakeet in Spain. The pest status of the species in its native range, together to its distribution trend, should be taken into account by wildlife agencies to consider options for management.