Overlap in reproductive phenology increases the likelihood of cavity nest usurpation by invasive species in a tropical city

Abstract

Multiple invasive cavity-nesting bird species can be present in a nest web, the network linking birds using cavities. We investigated the nest preferences and breeding phenologies of the cavity-nesting guild in the region surrounding Miami, Florida, USA, where invasive starlings, mynas, and parrots potentially usurp cavities from native woodpeckers and secondary cavity-nesters. We asked if the timing of reproduction determines which invasive species will usurp cavities from native birds with similar nest preferences. Nest usurpations between European Starlings (Sturnus vulgaris) and the woodpecker species present in Miami is well documented, but we predicted that a recently arrived sturnid species and introduced psittacids would also usurp nests. European Starlings had the largest breeding population of any species in our nest web, breeding during the peak of nesting season, and usurped the largest number of active nest cavities. We found that a small population of Common Mynas (Acridotheres tristis) usurped nests, sharing the peak-season nesting period with starlings and native woodpeckers. Parrots bred later than we expected, avoiding nest-site overlap with similarly large native birds that use cavities with similar characteristics. Parrots did not usurp any active nest cavities from native birds. Our results demonstrate how to use analysis of cavity characteristics and reproductive timing to evaluate threats to a cavity nest web posed by multiple invasive species. Common Myna currently usurp few nests; if they increase greatly in population, they could pose a problem for native cavity-nesters.

Noisy neighbours and myna problems: Interaction webs and aggression around tree hollows in urban habitats

“…However, the difference in mean body size did not predict the outcome of interactions between species pairs. This could be due to high overlap in body size between similarly sized species (Diamond & Ross, 2020). For example, the common myna (113 ± 30 g) won most of the interactions (26/29) with the rainbow lorikeet (126 ± 44 g), the native species closest in size.…”

“…Our work supports the results found by Pell and Tidemann (1997) who found that mynas displayed more aggression and occupied more tree hollows than native species. In North America, Diamond and Ross (2020) found that mynas competed most strongly with the similarly sized native red‐bellied woodpeckers Melanerpes carolinus and invasive common (European) starlings. It appears that overlap in body size and cavity preference are key indicators of their impact everywhere they are invasive.…”

“…We predicted that species with increasing overlap in their traits (body size and nest‐site preferences) would interact more frequently. We also predicted that the impacts of common myna aggression would be highest for similarly sized species (Diamond & Ross, 2020; Orchan et al., 2013).…”

“…Such traits can also influence the outcome of competitive interactions; for example, larger species often have a physical advantage in aggressive interactions (Jennions & Backwell, 1996; Miller et al., 2017; Petren & Case, 1996). Therefore, exploring the extent to which trait overlaps between invasive and native birds can provide some insight into which species within a community are more likely to be impacted by the increase in competition from the introduction of an invasive species (Diamond & Ross, 2020; Orchan, Chiron, Schwartz, & Kark, 2013).…”

“…Body mass is important as larger species are assumed to have an advantage in physical contests (Human & Gordon, 1996; Sol et al., 2012). Breeding‐niche reflects, in part, the nesting and habitat requirements for a given species, with increasing overlap in breeding‐niche positively correlated with increasing competition (Brazill‐Boast et al., 2010; Diamond & Ross, 2020). We predicted that species with increasing overlap in their traits (body size and nest‐site preferences) would interact more frequently.…”