A protective nesting association with native species counteracts biotic resistance for the spread of an invasive parakeet from urban into rural habitats

Abstract

Background: Non-native species are often introduced in cities, where they take advantage of microclimatic conditions, resources provided by humans, and competitor/predator release to establish and proliferate. However, native communities in the surrounding rural or natural areas usually halt their spread through biotic resistance, mainly via top-down regulative processes (predation pressure). Here, we show an unusual commensal interaction between exotic and native bird species that favours the spread of the former from urban to rural habitats. Results: We show how Monk parakeets Myiopsitta monachus, an invasive species often introduced in cities worldwide, associated for breeding with a much larger, native species (the white stork Ciconia ciconia) to reduce predation risk in central Spain, thus allowing their colonization of rural areas. Parakeets selected stork nests close to conspecifics and where breeding raptors were less abundant. Parakeets always flushed when raptors approached their nests when breeding alone, but stayed at their nests when breeding in association with storks. Moreover, when storks abandoned a nest, parakeets abandoned it in the following year, suggesting that storks actually confer protection against predators. Conclusions: Our results show how a protective-nesting association between invasive and native species can counteract biotic resistance to allow the spread of an invasive species across non-urban habitats, where they may become crop pests. Monk parakeet populations are now growing exponentially in several cities in several Mediterranean countries, where they coexist with white storks. Therefore, management plans should consider this risk of spread into rural areas and favour native predators as potential biological controllers.

Cryptosporidium spp. and Giardia spp. in Free-Ranging Introduced Monk Parakeets from Santiago, Chile

“…This possibility is supported by a recent report issued in Spain that describes how Monk Parakeets from Madrid have spread into rural areas where they have been detected nesting in association with White Storks (Ciconia ciconia). This type of behavior could allow parakeets to increase their invasive potential by avoiding biotic resistance in the form of predator pressure, for example [82]. Although White Storks are not present in Chile, parakeets could eventually benefit from the presence of other bird species and expand their range of distribution.…”

High Prevalence of Novel Beak and Feather Disease Virus in Sympatric Invasive Parakeets Introduced to Spain From Asia and South America

“…However, no test of the occurrence of the virus in the parakeets was conducted. Thus, the high prevalence of BFDV in the invasive parakeet populations sampled in southern Spain should be carefully considered, as it may have important consequences for the conservation of native birds, particularly those sharing habitats or nests with these invasive species and those predating on them both in urban and rural habitats [30,51,52]. These concerns increase due to the fast spread rates of these two parakeet species in Spain [19,53].…”

The Role of Monk Parakeets as Nest-Site Facilitators in Their Native and Invaded Areas

“…From 2013 to 2020, we monitored populations of monk parakeets established in different countries including the native (Argentina, Brazil, Paraguay, and Uruguay) and invaded range (Italy, Puerto Rico, and Spain) of the species (Figure 1a) in urban and rural ranges. This monitoring was conducted in different campaigns of extensive field work that covered both rural and urban habitats in the native, e.g., [31] and invaded ranges [9,[32][33][34] of monk parakeets, finding that the species is more abundant in rural areas in its native range, but proliferates more in urban areas in its invaded ranges. Once monk parakeet nests were located, we identified the substrate on which they were placed (tree or human construction), estimated their height above ground level (visually or using a laser rangefinder for heights > 10 m), and counted the number of chambers as a measure of nest size.…”

“…However, most studies on biotic relationships among non-native and native species have long been focused on antagonistic interactions (predation and competition), which are among the main factors of biodiversity loss [3][4][5][6]. Mutualistic and commensal interactions, which may be beneficial for both non-native and native species, have been poorly studied [7][8][9] and mostly focused on plants and invertebrates [7,10].…”