Population estimates of non-native rose-ringed parakeets Psittacula krameri (Scopoli, 1769) in the Durban Metropole, KwaZulu-Natal Province, South Africa

The Rose-ringed Parakeet Psittacula krameri is one of the world’s commonest invasive bird species and has established in the South African urban landscapes. However, relatively little is known about the feeding biology of parakeets here. We surveyed areas in eThekwini Municipality, Durban, South Africa, to determine their feeding sites and the related land-use types. Patterns of the association were explored using Correspondence Analysis to determine parakeets’ diet across seasons and interaction between different tree species fed on by parakeets and other bird species. Dietary items were determined visually using binoculars. We identified a total of 63 feeding sites with many in the urban built land-use cover type. The parakeets’ diet differed significantly across the seasons with spring accounting for 33% of annual food items. We identified 31 fruiting/flowering tree species fed on by the parakeets, with fleshy fruits and flowers accounting for 58% and 19%, respectively. Native tree species (63%) were mostly relied on when compared with non-native (27%). They also fed on carpenter ants Camponotus cinctellus which contributed 3% of their diet. The forest fever-berry Croton sylvaticus (fleshy fruits) and African star-chestnut Sterculia africana (flowers) were the most preferred tree species in autumn and summer. The observed number of bird species that communally fed with parakeets were significantly different across the sampled seasons. The diets for the Common Myna Acridotheres tristis and the Speckled Mousebird Colius striatus overlapped with parakeets for most tree species. Parakeets were observed actively feeding in the early mornings and late afternoons before roosting. Our study supports that parakeets are generalist-opportunistic feeders. The assessment of Rose-ringed Parakeets feeding ecology may help understand their potential impact on native tree and bird species within an urban landscape.

The Rose-ringed Parakeet Psittacula krameri has established feral populations in South African suburban areas. However, the information on the breeding biology of parakeets remains poorly documented in the country. We assessed parakeets’ breeding status and behaviour by locating their roost and breeding sites in Durban, eThekwini Metropole, KwaZulu-Natal province. We also placed artificial nest boxes to determine the occupancy of parakeets or other bird species. We identified 39 parakeet breeding sites with a total of 72 nests. There were no significant differences between the number of active parakeet nests in the first (n = 53 nests) and second breeding seasons (n = 59). Rose-ringed Parakeets used four tree species for nesting, with the white milkwood Sideroxylon inerme used the most (71%). Only East African lowland honey bees Apis mellifera scutellata and Common Mynas Acridotheres tristis used the artificial nest boxes. Parakeet fledgings recorded ranged between one and three per nest, and their numbers differed significantly between seasons. The number of fledglings was not influenced by any of the tree variables measured and distance or location. The distance between the parakeets’ roosting and breeding sites ranged from 1.43 to 5.0 km. Our study provides essential data for an overall management strategy, including eradication programs for this species in South Africa.

The Rose-ringed Parakeet Psittacula krameri (Scopoli, 1769) has become invasive in several countries, including South Africa, mainly through the pet trade releases and escapees. We conducted an online questionnaire survey targeting the residents in Durban, eThekwini Municipality, KwaZulu-Natal, South Africa. We aimed to determine the distribution, habitat and diet of the Rose-ringed Parakeet. We also determined if the public perceived parakeets as pests and if control measures were supported. We found that many parakeet sightings were reported in Durban North, primarily in and around shopping centres. Approximately 64.5% of respondents provided feeding stations for parakeets, with most providing seeds and grains. A total of 173 (55.4%) respondents considered parakeets as a pest. Rose-ringed parakeets were reported to chase nine bird species, of which seven were native and two non-natives. Most respondents stated that parakeets should not be controlled. However, most of those who supported their control suggested shooting and destruction of eggs. We concluded that the distribution of parakeets is likely expanding and associated with anthropogenic activities in this urban landscape. However, public perceptions may make invasive Rose-ringed Parakeet management difficult.

Background: Alien species are one of the major causes contributing to biodiversity loss. In Europe, over 340 alien bird species have been recorded in the wild, of which 74 are established. Among 12 established alien parrot species in Europe, the Rose-ringed Parakeet (RRP) Psittacula krameri is the most abundant and widespread. Objective: Although one of the best documented alien vertebrates in Europe, historical and current datasets on RRP invasion success and demography have not been systematically collated and analysed. This paper therefore aims to bring together, verify and make available this information. Method: Existing distribution and demographic data for the RRP in Europe were collated from the following sources: (a) literature search; (b) bird sighting databases; (c) regional bird experts; (d) RRP roost counts. With this data, we evaluated population size and growth per population, country and the whole of Europe in the period 1965-2015. Results: The RRP is well established in Europe with at least 90 breeding populations in 10 countries, and a total population size of at least 85,000 birds as of 2015. For Western Europe, long-term demographic data indicate the species has grown considerably in number, although some populations have failed to persist. Data is scarce for countries in Central, Eastern and Northern Europe. Conclusion: Our synthesis reveals a positive demographic trend across Europe, although locally, some populations appear to have reached carrying capacity. Further research is needed to understand the mechanisms underlying RRP population growth in Europe, and methods amenable to citizen-scientists are urgently required to monitor population and range dynamics.

In general, non-native bird species may competitively exclude native species from nest sites. The potential resource conflict between a native and an introduced bird species, the native European Starling (Sturnus vulgaris) and the introduced Asian Ring-necked Parakeet (Psittacula krameri), was inferred from hole occupancy in parks of the German Upper Rhine Valley (Wiesbaden, Mannheim, Schwetzingen, Edingen-Neckarhausen), where Ring-necked Parakeets have been known to occur for 15 to 35 years. Only 2.2 % of trees (n = 3487) had cavities with an entrance diameter ≥4 cm. The number of unoccupied tree holes was high, representing 71 % of 639 recorded cavities. A niche separation corresponding to tree size and tree species preferred by both bird species could be detected. Starling preferred trees with a diameter of 0.75 ± 0.30 m, whereas Ring-necked Parakeet favoured ones with 1.16 ± 0.36 m in diameter. Both bird species were the most abundant hole-nesters in the examined cavities. Ring-necked Parakeets preferred Platanus x hispanica, which hosted 57 % of all broods for the parakeet, but did not use Acer pseudoplatanus. Starling favoured Quercus robur with 25 % of all broods, followed by A. pseudoplatanus with 19 %. P. x hispanica showed the highest numbers of cavities with 227 in total and a median of 3 holes per tree, partially produced by Ring-necked Parakeet. The largest colony-in-one-tree in this study was 9 for P. krameri and 5 for S. vulgaris. In this study, Starlings took over two nests from Ring-necked Parakeets, with one case vice versa, and Honeybees took over one active Ring-necked Parakeet nest.

Amateur breeding of parrots as pets has contributed to many species being found in areas where they never occurred in the wild, particularly in warmer regions, but also in the temperate climates of North America and Europe. Climate change is likely to exacerbate this process. We hypothesised that parrots occurred in the wild in the cities of Poland, especially the rose-ringed parakeet, as there are reports of breeding sites in the literature. Using information on lost, found and sighted parrots posted on social media, we have analysed the extent of parrot emergence in Poland. In a period of less than two years (from October 2018, through 2019 and from June to the end of December 2021), 2,675 parrot specimens of 49 species were found in the wild. The most frequently observed species were cockatiel Nymphicus hollandicus (N = 962), budgerigar Melopsittacus undulatus (N = 884) and rose-ringed parakeet Psittacula krameri (N = 182). Parrots were most frequently observed in urban areas, in regions characterized by a higher population size, a higher income and a higher proportion of people with a university degree. Our study shows that the occurrence of parrots, especially rose-ringed parakeets in the wild, needs to be monitored as new breeding sites may appear.

In this report, we have examined the effects of lithium on testicular morphology in a male subtropical wild avian species, the roseringed parakeet (Psittacula krameri). Adult male birds were collected during the months of February-March, a time when the testicular gametogenic activity in these seasonally breeding birds is at its peak. They were injected, intramuscularly, twice daily (07:00 and 19:00 h) with lithium chloride (Sigma Chemical Company) at a dosage of 0.5 mEq/Kg body weight either for 5 or 10 days. A significant decrease in both the absolute and relative testicular weights was evident in the lithium-treated birds as compared to those of the saline-injected control animals. Light microscopic studies of the testis in the lithium-treated animals showed a wide range of degenerative changes. These included a) a significant reduction in the diameter of seminiferous tubules; b) necrosis and exfoliation of most of the germ cells in the seminiferous tubular lumen with the exception of the spermatogonia; and c) a significant reduction in the number of mature spermatozoa in the tubular lumen. These degenerative changes were dependent on the duration of lithium treatment and were evident when the plasma lithium concentrations were well below the human therapeutic range. Leydig cell morphology was not affected by lithium however. Our results provide the first experimental evidence of lithium's adverse reproductive function in an avian species. These data provide further support to the view that lithium adversely affects the male reproductive system and that these effects extend beyond mammalian species.

Seasonal effects on the thermoregulation of invasive rose-ringed parakeets (Psittacula krameri)

Certain traits of recipient environments, such as the availability of limiting resources, strongly determine the establishment success and spread of non-native species. These limitations may be overcome through behavioral plasticity, allowing them to exploit alternative resources. Here, we show how a secondary cavity nester bird, the rose-ringed parakeet Psittacula krameri, innovates its nesting behavior as a response to the shortage of tree cavities for nesting in its invasive range in Tenerife (Canary Islands). We observed that some breeding pairs excavated their own nest cavities in palms, thus becoming primary cavity nester, whereas others occupied nests built with wood sticks by another invasive species, the monk parakeet Myiopsitta monachus. The use of these novel nesting strategies increased the number of breeding pairs by up to 52% over 6 years, contributing to a 128.8% increase of the whole population. Innovative nests were located at greater heights above ground and were more aggregated around conspecifics but did not result in greater breeding success than natural cavities. Occupation of monk parakeet colonies by rose-ringed parakeets also benefited the former species through a protective-nesting association against nest predators. Our results show how an invasive species innovate nesting behaviors and increase nest-site availability in the recipient environment, thus facilitating its population growth and invasion process. Potential behavioral innovations in other invasive rose-ringed parakeet populations may be overlooked, and should be considered for effective management plans.

The Rose-ringed Parakeet (Psittacula krameri) was recorded in Turkey for the first time in 1975 and has since then established breeding populations in at least six cities as a consequence of intentional and accidental introductions. Parakeet sightings have been recorded in and around urban areas and records are available from 26 provinces. It is most abundant in İstanbul, followed by İzmir, Ankara, Yalova, Antalya, and Şanlıurfa. The distribution and population size has increased continuously especially since the mid-2000s. The population is estimated to be now over 1,355 individuals in the country, which is still moderate compared to some other West European countries.

The role of the pineal gland and its hormone melatonin in the regulation of annual testicular events was investigated for the first time in a psittacine bird, the roseringed parakeet (Psittacula krameri). Accordingly, the testicular responsiveness of the birds was evaluated following surgical pinealectomy with or without the exogenous administration of melatonin and the experimental manipulations of the endogenous levels of melatonin through exposing the birds to continuous illumination. An identical schedule was followed during the four reproductive phases, each characterizing a distinct testicular status in the annual cycle, namely, the phases of gametogenic quiescence (preparatory phase), seasonal recovery of gametogenesis (progressive phase), seasonal initiation of sperm formation (pre‐breeding phase), and peak gametogenic activity (breeding phase). In each reproductive phase, the birds were subjected to various experimental conditions, and the effects were studied comparing the testicular conditions in the respective control birds. The study included germ cell profiles of the seminiferous tubules, the activities of steroidogenic enzymes 17β‐hydroxysteroid dehydrogenase (17β‐HSD), and Δ53β‐hydroxysteroid dehydrogenase (Δ53β‐ HSD) in the testis, and the serum levels of testosterone and melatonin. An analysis of the data reveals that the pineal gland and its hormone melatonin may play an inhibitory role in the development of the testis until the attainment of the seasonal peak in the annual reproductive cycle. However, in all probability, the termination of the seasonal activity of the testis or the initiation of testicular regression in the annual reproductive cycle appears to be the function of the pineal gland, but not of melatonin.

Rose-ringed parakeets (Psittacula krameri) are one of the most widespread invasive avian species worldwide. This species was introduced to the island of Kaua‘i, Hawai‘i, USA, in the 1960s. The rapidly increasing population has caused substantial economic losses in the agricultural and tourism industries. We evaluated the efficacy of a roost culling program conducted by an independent contractor from March 2020 to March 2021. We estimated island-wide minimum abundance was 10,512 parakeets in January 2020 and 7,372 in April 2021. Over 30 nights of culling at four roost sites, approximately 6,030 parakeets were removed via air rifles with 4,415 (73%) confirmed via carcasses retrieval. An estimated average of 45 parakeets were removed per hour of shooter effort. The proportion of adult females removed in 2020 was 1.9 × greater when culled outside of the estimated nesting season. Of the four roosts where culling occurred, the parakeets fully abandoned three and partially abandoned one site. Of the three fully abandoned roosts, an estimated average of 29.6% of birds were culled prior to roost abandonment. The roost culling effort was conducted during the COVID-19 pandemic, when tourist numbers and foot traffic were greatly reduced. It is unknown how public perception of roost culling in public areas may impact future efforts. Findings suggest roost culling can be utilized for management of nonnative rose-ringed parakeet populations when roost size is small enough and staff size large enough to cull entire roosts in no greater than two consecutive nights (e.g., if two shooters are available for three hours per night, roost culling should only be attempted on a roost with ≤ 540 rose-ringed parakeets).

Psittaciformes play a predominant role among the exotic species deliberately imported by humans all over the world, being the most popular bird pets. When released, they often establish naturalized populations, as they present a wide ecological plasticity and synanthropy. As for Tuscany, eight species have been reported (42.11% of those reported for the whole Italy), often near urban centers. Among those, two are possibly established and expanding: the rose-ringed parakeet (Psittacula krameri) and the monk parakeet (Myiopsitta monachus). This work aims to statistically reconstruct the actual extent of occurrence (EOO) of these two species through a fixed kernel method and their potential distribution through a bioclimatic envelope (BIOCLIM), using variables selected from the WORLDCLIM database, selected according to the ecological requirements of these species. BIOCLIM analysis suggests a possible expansion risk for monk parakeet and rose-ringed parakeet in Tuscany, as both species are presented with a huge amount of suitable but not occupied habitat. In particular, rose-ringed parakeet may colonize the inner part of the region, while the southern part of the region may be exposed to a possible range expansion of monk parakeet.

Over 60 out of 355 currently living parrot species have established at least one breeding population outside their natural distribution ranges. Among those, the ring-necked parakeet is one of the most successful invaders. This species is a gregarious Afro-Asian parakeet with an extremely large distribution range, recorded in over 35 countries outside its native extent of occurrence. Despite being one of the most introduced bird species throughout the world, its interactions with native biodiversity and environment are not completely known and rely mainly on anecdotal evidence. Future researchers are therefore required to fill these gaps. Trunk cavities represent the preferred breeding sites of these alien parrots and indicate potential routes of direct and indirect competition with native hole-nesting bird species, such as nuthatches and starlings. Interactions with tree squirrels, bats and insects are rarely reported but may be more severe than currently known. Droppings by ring-necked parakeets may alter the herbaceous vegetation under the roost but direct cause–effect relationships for this phenomenon are hard to assess if no data about floral composition before the time of invasion is available. Ring-necked parakeets may have economic impacts, being responsible for crop damage, as well as societal impacts; three bird strikes with airplanes involved this species in England. The ring-necked parakeet is a potential reservoir of a plethora of diseases transmittable to humans and wildlife. No data concerning ecosystem recovery after the removal of ring-necked parakeets is available, as eradication and numerical control programmes are often hampered by the emotional affiliation which links humans to these bright birds.

Gut microbial communities play a fundamental role in health and disease, but little is known about the gut microbiota of pet bird species. This is important to better understand the impact of microbes on birds’ health but may also be relevant in a context of zoonoses. Total genomic DNA samples from pooled fecal samples from 30 flocks (4–7 pet birds per flock) representing over 150 birds of six different species (two Passeriformes: Northern Mockingbird (Mimus polyglottos) and Zebra Finch (Taeniopygia guttata), and four Psittaciformes: Lovebird (Agapornis, different species), Cockatiel (Nymphicus hollandicus), Red-rumped Parrot (Psephotus haematonotus), and Rose-ringed Parakeet (Psittacula krameri) were used for 16S rRNA gene analysis. Several taxa were found to be different among the bird species (e.g., lowest median of Lactobacillus: 2.2% in Cockatiels; highest median of Lactobacillus: 79.4% in Lovebirds). Despite marked differences among individual pooled samples, each bird species harbored a unique fecal bacterial composition, based on the analysis of UniFrac distances. A predictive approach of metagenomic function and organism-level microbiome phenotypes revealed several differences among the bird species (e.g., a higher proportion of proteobacteria with the potential to form biofilms in samples from Northern Mockingbirds). The results provide a useful catalog of fecal microbes from pet birds and encourage more research on this unexplored topic.