Biology and Impacts of Pacific Island Invasive Species. 15. Psittacula Krameri, the Rose-Ringed Parakeet (Psittaciformes: Psittacidae)1
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Biology and Impacts of Pacific Island Invasive Species. 15. Psittacula krameri, the Rose-Ringed Parakeet (Psittaciformes: Psittacidae)1 Aaron B. Shiels,2,4 and Nicholas P. Kalodimos3 Abstract: The rose-ringed parakeet (RRP), Psittacula krameri, has become established in at least four Pacific Island countries (Hong Kong China, Japan, New Zealand, U.S.A.), including the Hawaiian islands of Kaua‘i, O‘ahu, and Hawai‘i. Most Pacific islands are at risk of RRP colonization. This species was first introduced to Hong Kong in 1903 and Hawai‘i in the 1930s–1960s, established since 1969 in Japan, and in New Zealand since 2005 where it has repeatedly established after organized removals. The founding birds were imported cage-birds from the pet trade. In native India, RRP are generally found associated with human habitation and are considered a severe agricultural pest. In the Hawaiian Islands, RRP are increasing and expanding their geographic ranges below 500 m elevation. Population estimates in 2018 on Kaua‘i were ∼6,800 birds, which was a three-fold increase and a 22.5% annual growth rate in the prior 6 years, whereas O‘ahu had ∼4,560 birds with a 21% annual growth rate the prior 9 years; these rates suggest a population doubling time of ∼3.5 years. Wild RRP can live 14+ years, can reproduce after 1.5 years, and have few effective predators. Breeding pairs produce 1–3 fledglings annually. RRP are seed predators and rarely seed dispersers; their flock-foraging behavior can result in severe damage to orchard and field agricultural crops including tropical fruit and corn (Zea mays), and such economic damages are especially pronounced on Kaua‘i. Island societies should prevent new introductions and consider RRP deterrents and population control methods to protect resources. Keywords: agricultural crop and orchard loss, economic costs, human-wildlife interaction, parrot damage management, pest eradication, pet trade, ring-necked parakeet, urban bird ecology PSITTACULA KRAMERI, THE ROSE-RINGED or ring- necked parakeet, has been introduced to over 1Manuscript accepted 13 August 2019. 2 40 countries, gaining its status as the most USDA, APHIS, National Wildlife Research Center, widely introduced parrot in the world. 4101 LaPorte Avenue, Fort Collins, CO 80521, USA. 3University of Hawai‘i at Manoa, 1910 East West Although regarded as a strikingly beautiful Road, Honolulu, HI 96822, USA. bird by many people, this species is a severe 4Corresponding author (e-mail: aaron.b.shiels@usda. agricultural pest that establishes and repro- gov). duces rapidly, aggregates nightly in large roosts in human-inhabited areas, and is Pacific Science (2019), vol. 73, no. 4:421–449 disruptive to humans via its noise and fecal doi:10.2984/73.4.1 pollution. Aside from a few locations in This article was created by a U.S. government northern Europe where some of the public employee and is on the Public Domain. Public domain cherish this species in the wild (Menchetti information may be freely distributed and copied, but it is requested that in any subsequent use the U.S. et al. 2016, Crowley et al. 2019), rose-ringed Department of Agriculture and the journal, Pacific parakeets are generally unwanted invaders Science, be given appropriate acknowledgment. where they have established. 421 422 PACIFIC SCIENCE • October 2019 Rose-ringed parakeets are native to the parakeet, and Senegal long-tailed parakeet. tropical and subtropical parts of Africa and The official American Ornithologists Union Asia, but they have established, expanded, and common name is rose-ringed parakeet. persisted in both tropical and temperate The rose-ringed parakeet (RRP) is classi- regions of the world (Butler 2005). On Pacific fied into four geographically distinctive sub- islands, four countries (Hong Kong China, species of which only the South Asian Japan, New Zealand, and U.S.A.) have subspecies, P. krameri manillensis (Bechstein, established rose-ringed parakeet populations; 1800) and P. k. borealis (Neumann, 1915), are however, most islands in the Pacific— thought to be naturalized in the State of specifically islands from southern Canada to Hawai‘i(Pyle and Pyle 2009, N.P.K., pers. central Chile in the eastern Pacific, to islands obs.), Hong Kong, Japan, and New Zealand; from northern Japan to central New Zealand genetically these two subspecies are the most in the western Pacific—are potentially at risk represented across worldwide RRP popula- of rose-ringed parakeet colonization. The tions (Strubbe and Matthysen 2009a), and climate and latitudinal ranges (ca. 56° Nto their predominance correlates with the higher 44° S) of these Pacific islands match the ranges numbers transported outside their native where they have established elsewhere in the range via the pet trade (Jackson et al. 2015). world. Islands with human habitation are most These South Asian subspecies are not easily at risk of rose-ringed parakeet establishment distinguishable from one another, but have (Strubbe et al. 2015), as humans often enhance subtle morphometric differences and geo- habitat (e.g., by planting trees used by graphic origins; P. k. manillensis originates parakeets for nesting and feeding) and provide south of latitude 20° N in India and in Sri bird feeders. This species’ prevalence in the Lanka, whereas P. k. borealis originates north pet trade and in zoos increases the chances of of 20° N in India, as well as in Pakistan, its wild establishment by escaping, or being Bangladesh, Nepal, and Myanmar (Juniper released, from cages (Reino et al. 2017, Avery and Parr 1998, Menchetti et al. 2016). The and Shiels 2018). two African subspecies are P. k. krameri While few data on non-native parrots exist (Scopoli, 1769) and P. k. parvirostris (Souance, for Pacific islands (Runde et al. 2007), our review 1856), and to our knowledge they have not draws on studies of the rose-ringed parakeet naturalized in the Pacific region. Psittacula k. from both its non-native range in the Pacific and krameri is from the equatorial regions in other parts of the world and its native Indian central and western Africa, and is found range. Due to the rapid increases in population in Guinea, Senegal, and southern Mauritania growth and damage resulting from this species in the east, to western Uganda and southern during the last 5–10 years in Hawai‘i, we feel this Sudan (Juniper and Parr 1998). Psittacula k. review is particularly timely to both prevent parvirostris is limited to the eastern equatorial more islands from being colonized by these region of the African continent—northwest invasive birds, and to motivate population Somalia west across northern Ethiopia to the management to help reduce and prevent future Sennar district of Sudan. These two African damage and economic losses. subspecies were exported in lesser numbers and are not naturalized in the Pacific; they were recorded as being wild-living in Puerto NAME AND DESCRIPTION Rico (Atlantic Ocean) but they failed to Species Description establish (M. Oberle, pers. comm.). Psittacula krameri is in the Class: Aves, Order: Psittaciformes, Family: Psittacidae, Subfamily: Intra-Specific Variation Psittacinae, Genus: Psittacula (Cuvier, 1800). The African subspecies differ physically from Some common English names for this species the two Indian subspecies in being smaller and are: green long-tailed parakeet, long-tailed lighter green with a yellow wash throughout. parakeet, ring-necked parakeet, rose-ringed The facial area is light yellow-green and Psittacula krameri, Pacific Island Invasive Species • Shiels and Kalodimos 423 contrasts with the more intense grey-blue Distinguishing Features wash to the posterior head and nape. African subspecies’ bills are smaller and dark red or Psittacula k. manillensis is a 38–42 cm long maroon distally grading to black in contrast to (body + tail) parrot, with its tail accounting for the larger red bills of the Indian subspecies about half of its length (∼25 cm; Butler 2005). (Forshaw 1989, Juniper and Parr 1998). In Europe, adult RRP generally weigh about Pithon and Dytham (2001) examined 180 140 g (Butler and Gosler 2004). RRP on Kaua‘i museum specimens of RRP and determined averaged 133 g, but 12 of the 17 individuals that body length and bill length were the weighed were juveniles; the four adult males parameters that were most likely to differ averaged 139 g (Gaudioso et al. 2012). RRP are among the four subspecies of RRP, and toe generally uniform light emerald green and the and wing length were also helpful in upper and lower mandibles of the bill are red. distinguishing some of the subspecies. Thus, Likeallparrots, RRP have zygodatyl feet—they there are subtle morphometric differences have two forward-pointing and two backward- among the four subspecies, but due to P. k . pointing toes—are brightly colored, possess manillensis being the most common species shortand stoutstrongly hookedbeaks, and have introduced, including throughout the Pacific, relatively short legs (Figure 1). we have focused our review on this sub- RRP are sexually dichromatic, with the species. most obvious characteristic distinguishing FIGURE 1. Rose-ringed parakeets (Psittacula krameri) on an ironwood tree (Casuarina equisetifolia) adjacent to Kapi‘olani Park, O‘ahu, Hawai‘i. The upper two individuals are males (notice distinctive dark ring around neck), and the lower individual is a presumed adult female (notice faint green ring around neck, and shorter tail). The uppermost bird is a rare blue variety, with no more than three individuals known on O‘ahu. Photograph by Phil Taylor. 424 PACIFIC SCIENCE • October 2019 adult males from females being that males Hong Kong and Japan have non-native possess a black ring around their neck. The Alexandrine parakeet (Psittacula eupatria) black ring extends from the chin to both sides established, which is a close relative of the of the head, and a thin rose-colored ring is RRP (diverging from a common ancestor present under the black ring around the nape.