Exotic parrots breeding in urban tree cavities: nesting requirements, geographic distribution, and potential impacts on cavity nesting birds in southeast Florida

Background Exotic parrots have established breeding populations in southeast Florida,including several species that nest in tree cavities. We aimed to determine the species identity,nest site requirements,relative nest abundance,geographic distribution,and interactions of parrots with native cavity-nesting bird species.

Methods We searched Miami-Dade County,Florida,and nearby areas for natural cavities and holes excavated by woodpeckers,recording attributes of potential nest trees. We inspected all cavities with an elevated video inspection system to determine occupancy by parrots or other birds. We mapped nearly 4000 citizen science observations of parrots in our study area corresponding to our study period,and used these to construct range maps,comparing them to our nesting observations.

Results Not all parrots reported or observed in our study area were actively breeding. Some parrots were observed at tree cavities,which previous studies have suggested is evidence of reproduction,but our inspections with an elevated video inspection system suggest they never initiated nesting attempts. Several parrot species did successfully nest in tree cavities,Red-masked Parakeets (Psittacara erythrogenys) and Orange-winged Parrots (Amazona amazonica) being the most common (n = 7 and 6 nests,respectively). These two parrots had similar nesting requirements,but Orange-winged Parrots use nests with larger entrance holes,which they often enlarge. Geographic analysis of nests combined with citizen science data indicate that parrots are limited to developed areas. The most common parrots were less abundant cavity nesters than the native birds which persist in Miami's urban areas,and far less abundant than the invasive European Starling (Sturnus vulgaris).

Conclusions Exotic parrots breeding elsewhere in the world have harmed native cavity-nesting birds through interference competition,but competitive interference in southeast Florida is minimized by the urban affinities of parrots in this region. The relative abundance and geographic distribution suggest that these parrots are unlikely to invade adjacent wilderness areas.