Abstract
BackgroundExotic 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.MethodsWe 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.ResultsNot 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).ConclusionsExotic 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.
Highlights
Exotic parrots have established breeding populations in southeast Florida, including several species that nest in tree cavities
Most research on the role of exotic parrots in cavity nest webs has been conducted on Rose-ringed Parakeets (Psittacula krameri) in Europe, which compete with native birds and mammals for nest cavities (Runde et al 2007; Strubbe and Matthysen 2007, 2009; Czajka et al 2011; Newson et al 2011; Mori et al 2013, 2017; Hernández-Brito et al 2014, 2018; Peck et al 2014)
The goals of our study were (1) to identify species of exotic parrots that breed in tree nest cavities, (2) to compare the nesting requirements of the most common parrot species, (3) to compare the abundance of parrot nests found in trees vs. nests of other cavity-nesting birds, and (4) to determine if, based on their relative abundance, geographic distribution, and interactions with other cavity-nesting birds, tree-nesting parrots pose a threat to the native cavity nesting guild in natural areas outside of the urban matrix
Summary
Exotic parrots have established breeding populations in southeast Florida, including several species that nest in tree cavities. Southeast Florida is a global hotspot for invasive exotic fauna of all sorts, including birds (Simberloff et al 1997; Sementelli et al 2008; Mutascio et al 2018; Clements et al 2019). This research has generally concluded that the Rose-ringed Parakeet has reduced populations of native species though interference competition This parrot is not a breeding resident in southeast Florida, but several other parrot species are participants in cavity nest webs in Miami, using woodpecker holes for reproduction
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