When ‘bullies’ come out of cities: mobbing among introduced Rose-Ringed Parakeets Psittacula krameri and native species of conservation concern in extra-urban habitats with suggestions for a framework of PSIR indicators

Among avian invasive species, the Rose-Ringed Parakeet (or Ring-Necked Parakeet) Psittacula krameri is one of the most widely introduced birds in the world: this species originates from India and Africa and has established populations worldwide (Pârâu et al. 2016), colonizing mainly urban parks, where it can compete with many native species (Le Louarn et al. 2016). Nevertheless, in the last several years there has been evidence of its expansion into extra-urban areas (Pârâu et al. 2016). Although in urban environments the presence of RoseRinged Parakeet represents a still relatively limited factor of stress, on both ornamental plants and native animals, in extra-urban areas its presence is causing alarm, due to the possible ecological and economic impacts (e.g. in agriculture; Battisti and Fanelli 2022), analogously to the situation with other expanding parakeets (such as Monk Parakeet, Myiopsitta monachus; Di Santo, Battisti, and Bologna 2017; Postigo et al. 2017). Regarding ecological impacts, Rose-Ringed Parakeet may act with antagonistic competitive behaviours, which can culminate in fatal attacks, towards many animal species, mainly approaching the nests (or, secondarily, in foraging areas), since parakeets nest in a loosely colonial fashion and actively protect their eggs and chicks against predators (Peck et al. 2014). In this regard, evidence of competitive behaviours and lethal attacks have been observed between RoseRinged Parakeets and homeothermic vertebrates: bats (e.g. Nyctalus leisleri, Italy: Menchetti, Scalera, and Mori 2014; Nyctalus lasiopterus, Spain: Hernández–Brito et al. 2014a, 2018), rats (Rattus rattus, Spain: Hernández– Brito et al. 2014a), and squirrels (Sciurus vulgaris, France Clergeau, Vergnes, and Delanoue 2009; Italy: Fraticelli 2014; Sciurus anomalus, Turkey; Per 2018; see also Mori et al. 2013). Outside Europe, competitive events involving introduced parakeets are known also towards marsupials (e.g. Didelphis marsupialis, Venezuela, South America: Sainz-Borgo 2016). Among birds, there is much evidence of competition, mainly for suitable nesting sites, between parakeets and, mainly, treeand/or building-cavity nesters (Menchetti, Scalera, and Mori 2014, 2016), both in native-range and introduced-range countries (Khan 2012). In non-native areas, Starling (Sturnus vulgaris) represents the species most impacted by events of territorial or preemptive interference competition (FERA 2010; Czajka, Braun, and Wink 2011; Dodaro and Battisti 2014; Le Louarn et al. 2016; Şahin and Arslangündoğdu 2019). However, Eurasian Collared Dove (Streptopelia decaocto), domestic pigeons (Columba livia domestica), woodpeckers (e.g. Syrian Woodpeckers Dendrocopos syriacus: Şahin and Arslangündoğdu 2019), crows (e.g. Jackdaw, Corvus monedula: Le Louarn et al. 2016; Gereschi, Galli, and Borgo 2022), Hoopoes (Upupa epops; Yosef, Zduniak, and Żmihorski 2016), and small passerines such as Great Tits (Parus major), Blue Tits (Cyanistes caeruleus), House Sparrows (Passer domesticus), Common Chaffinches (Fringilla coelebs), European Robins (Erithacus rubecula), Nuthatches (Sitta europaea) and others (probably: Swift, Apus apus, and Pale Swift, Apus pallidus; Grandi, Menchetti, and Mori 2018) can also suffer these competitive events in European and Middle Eastern urban parks (Le Louarn et al. 2016, 2018; Strubbe and Matthysen 2009; Strubbe, Matthysen, and Graham 2010; Peck et al. 2014; Covas et al. 2017; Şahin and Arslangündoğdu 2019). Regarding small passerines, avoidance behaviour between parakeets and small birds have also been recorded (Bednekoff and Houston 1994).