Effects of the Recent World Invasion by Ring-Necked Parakeets Psittacula krameri

Abstract

Over 60 out of 355 currently living parrot species have established at least one breeding population outside their natural distribution ranges. Among those, the ring-necked parakeet is one of the most successful invaders. This species is a gregarious Afro-Asian parakeet with an extremely large distribution range, recorded in over 35 countries outside its native extent of occurrence. Despite being one of the most introduced bird species throughout the world, its interactions with native biodiversity and environment are not completely known and rely mainly on anecdotal evidence. Future researchers are therefore required to fill these gaps. Trunk cavities represent the preferred breeding sites of these alien parrots and indicate potential routes of direct and indirect competition with native hole-nesting bird species, such as nuthatches and starlings. Interactions with tree squirrels, bats and insects are rarely reported but may be more severe than currently known. Droppings by ring-necked parakeets may alter the herbaceous vegetation under the roost but direct cause–effect relationships for this phenomenon are hard to assess if no data about floral composition before the time of invasion is available. Ring-necked parakeets may have economic impacts, being responsible for crop damage, as well as societal impacts; three bird strikes with airplanes involved this species in England. The ring-necked parakeet is a potential reservoir of a plethora of diseases transmittable to humans and wildlife. No data concerning ecosystem recovery after the removal of ring-necked parakeets is available, as eradication and numerical control programmes are often hampered by the emotional affiliation which links humans to these bright birds.