Factors affecting invasion process of a megadiverse country by two exotic bird species

Understanding the factors underlying bird invasions is crucial for their management. Here, the invasion processes of Mexico by the European Starling (Sturnus vulgaris) and the Eurasian Collared-Dove (Streptopelia decaocto) are analyzed. A 30 x 30 km grid-cell map with the presence/absence of both species was generated using citizenscience data to describe their invasion patterns in time and space from their first records until 2016. Binomial Generalized Linear Models were used to determine the invasion probabilities of both species. Geographic Information was used to determine the climatic variables that better explain their presence (abiotic factors) and the number of phylogenetically closely-related species (biotic factors). A bioclimatic model was used to test if the role that climatic variables play to determine the invasion success of birds at the global scale holds at regional scales. This model related the invasion probabilities of each species with biotic and abiotic factors. The main findings are: (1) Both species have expanded from established populations in the US, and new introductions by bird-trade. (2) European Starlings invaded the country slower than Eurasian Collared-Doves. (3) European Starlings invaded areas with dry and temperate climates, while Eurasian Collared-Doves invaded most of the country, being positively affected by temperature and precipitation. (4) Invasion probabilities of both species were not constrained by phylogenetically closely-related species richness. This study indicates that for exotic invasive birds that exploit agricultural areas, biotic factors do not provide invasion resistance of megadiverse countries such as Mexico.