Evaluating the population-level impact of an invasive species, Ring-necked Parakeet Psittacula krameri, on native avifauna

The introduction of exotic species to ecosystems can have severe consequences for populations of native organisms, but logistical limitations and shortage of historical data often hinder attempts to quantify the ecological implications of such relationships. The establishment and rapid expansion of Ring-necked Parakeets Psittacula krameri in England therefore presents a rare opportunity to apply novel analytical methods to existing extensive national bird monitoring data from the UK Breeding Bird Survey for an invasive species. A previous study from Belgium suggests that Ring-necked Parakeets have the potential to reduce the abundance of Eurasian Nuthatch Sitta europaea through competition for nesting cavities. Our analysis provides no evidence for a significant impact through competition on Nuthatch populations or those of any other cavity-nesting species within the Parakeet's current range in the UK. However, we cannot exclude the possibility that competitive exclusion could be occurring at a minority of sites at which availability of nest cavities is limiting. This may yet have significant implications for future conflict if Parakeets continue to increase in numbers and range.