‘The early bird catches the nest’: possible competition between scops owls and ring‐necked parakeets

Abstract

Competition for critical resources is one of the key mechanisms through which invasive species impact on native communities. Among birds, the widely introduced ring-necked parakeet Psittacula krameri locally affects cavity-nesting communities through competition for suitable tree cavities, although it remains unclear to what extent such competition translates into population declines of native species. Here, we studied the potential for nest site competition between ring-necked parakeets and the native scops owl Otus scops, a small nocturnal migratory raptor, by comparing the spatial distribution of the nest site locations of the raptor before (2002) and after (2015) the parakeet invasion. Pre-invasion nesting sites of scops owls (2002) strongly coincided with those selected by ring-necked parakeets, but although both parakeet and scops owl populations increased during the study period, this was no longer true for 2015. Ring-necked parakeets took over several cavities formerly occupied by scops owls, and land-use data suggest that because of the higher overall breeding densities in 2015, scops owls were forced to occupy suboptimal breeding habitats to minimize nest site competition with invasive parakeets. Ring-necked parakeets start breeding early in the season, a behaviour enabling them to secure the best nest sites first, before the owls return from their wintering grounds. Our study highlights that locally observed competition not necessarily impacts on population dynamics of competing species and thus warns against uncritical extrapolation of smaller scale studies for assessing invasive species risks at larger spatial scales. Nonetheless, given the increasing number of studies demonstrating its competitive capacities, monitoring of ring-necked parakeet populations is prudent and mitigation measures (such as mounting of man-made nest-boxes, which are used by scops owls, but not by parakeets) may be justified when the parakeets are likely to invade areas harbouring cavity-nesters of conservation concern.

From the cage to the wild: Introductions of Psittaciformes to Puerto Rico

“…Although there are concerns that mites may be vectors for diseases among parrots, most feather mites are considered ecto-commensals and feed on the oils produced by the birds (Blanco et al, 2001). Competition for nesting cavities is a major cause of concern because there are native species which depend on this scarce resource, and psittacine secondary cavity nesters can be aggressive competitors (Snyder et al, 2007;Strubbe & Matthysen, 2009a;Orchan et al, 2012;Mori et al, 2017). Currently, populations of non-indigenous cavity nesters (e.g., Amazona spp.…”

'Some like it alien': predation on invasive ring–necked parakeets by the long–eared owl in an urban area

“…The ring-necked parakeet in the study area A pair of RNP was first observed in Follonica in 1999 and the population peaked at 30-35 individuals in 2016 (Pârâu et al, 2016;Mori et al, 2017). In winter 2017, a group of eight long-eared owls established a roost at a distance of about 300 m from the parakeet roost.…”

“…The mean annual temperature was 16.8 ºC, with annual precipitation of 650-700 mm (Mori et al, 2017). This urban area is surrounded by farmland, mainly cereal and sunflower fields) and wide coastal pinewood forests with Pinus pinea (Mori et al, 2017). The first control site was located in the southern peripheral area of the city of Grosseto (42.77 ºN, 11.13 ºE: 14-18 m a.s.l.…”

“…black rats and birds (Mori and Bertolino, 2015). In a recent study in Follonica in central Italy (Mori et al, 2017), it was reported that the population of RNPs declined notably after a winter roost in 2017 following the establishment of the long-eared owl in the immediate surroundings of the parakeet roost. The aim of present study, therefore, was to analyze the winter diet of the long-eared owl in this urban area to quantify the level of predation on RNPs.…”

From the cage to the wild: Introductions of Psittaciformes to Puerto Rico with emphasis on the invasive ecology of the white-winged parakeet

“…Snyder, Wieley & Kepler, 2007;Strubbe & Matthysen, 2009a;Orchan et al, 2012;Mori et al, 2017).However, populations of cavity nesters (e.g., Amazona spp and rose-ringed parakeets) are relatively low, and the most successful psittacine species in Puerto Rico build their own nests. Finally, based on the distribution of Amazona spp.…”