Wetenschappelijk artikelRose-ringed parakeet Psittacula krameri populations and numbers in Europe: a complete overview.

Background: Alien species are one of the major causes contributing to biodiversity loss. In Europe, over 340 alien bird species have been recorded in the wild, of which 74 are established. Among 12 established alien parrot species in Europe, the Rose-ringed Parakeet (RRP) Psittacula krameri is the most abundant and widespread. Objective: Although one of the best documented alien vertebrates in Europe, historical and current datasets on RRP invasion success and demography have not been systematically collated and analysed. This paper therefore aims to bring together, verify and make available this information. Method: Existing distribution and demographic data for the RRP in Europe were collated from the following sources: (a) literature search; (b) bird sighting databases; (c) regional bird experts; (d) RRP roost counts. With this data, we evaluated population size and growth per population, country and the whole of Europe in the period 1965-2015. Results: The RRP is well established in Europe with at least 90 breeding populations in 10 countries, and a total population size of at least 85,000 birds as of 2015. For Western Europe, long-term demographic data indicate the species has grown considerably in number, although some populations have failed to persist. Data is scarce for countries in Central, Eastern and Northern Europe. Conclusion: Our synthesis reveals a positive demographic trend across Europe, although locally, some populations appear to have reached carrying capacity. Further research is needed to understand the mechanisms underlying RRP population growth in Europe, and methods amenable to citizen-scientists are urgently required to monitor population and range dynamics