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

Abstract

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.

Nest‐boxes alter the reproductive ecology of urban cavity‐nesters in a species‐dependent way

“…In many cities, nest-boxes are offered as a conservation measure to increase breeding opportunities for birds, and are perceived as human facilitation -a positive interaction to promote species diversity (Hacker & Gaines, 1997;Tomasevic & Marzluff, 2017). In some cases this is beneficial, increasing breeding probability (Sumasgutner et al, 2020), but on the other hand increasing local densities may boost competition among birds using the same type of nest (Diamond & Ross, 2019;Newton, 1994). Moreover, the numbers of dominant species can affect the numbers and distribution of other birds, especially in secondary forests.…”

Application of the Socio-Economic Impact Classification for Alien Taxa (SEICAT) to a global assessment of alien bird impacts

“…This is likely to be because parrots often possess high levels of urban tolerance (Maklakov et al 2011), facilitating their establishment in urban areas (e.g. Diamond and Ross (2019)). This may explain the general prevalence of parrot species in our dataset (Figure 1).…”

Temporally Separated Data Sets Reveal Similar Traits of Birds Persisting in a United States Megacity

“…It may be that more successful urban nesters would be those species that are able to utilize a variety of built structures (as well as natural cavities), including eaves of buildings, parking garages, and overpasses, with this flexibility allowing them to switch between substrates when one is not available. It is also possible that aggressive (urban-tolerant) cavity nesters such as European Starlings (Sturnus vulgaris) and/or parrots may be displacing natural cavity nesters within urban areas, though direct evidence of this is lacking (Koch et al, 2012;Diamond and Ross, 2019). Still, avian diversity in urban areas could be enhanced by provisioning artificial nesting structures, and maintaining natural nesting sites such as dead trees (see Tomasevic and Marzluff, 2017), as well as by retaining patches of natural habitat of various sizes within the urban matrix (Silva et al, 2015) and by planting a diversity of trees and shrubs as part of landscaping (Wood and Esaian, 2020).…”