Vertical segregation by breeding ring-necked parakeets Psittacula krameri in northern Italy

How far will they go? Considerations on the potential expansion of the Ring-necked Parakeet (<em>Psittacula krameri</em>) and Monk Parakeet (<em>Myiopsitta monachus</em>) in Veneto region (Italy) with MaxEnt distribution models

Predictive models of species distribution, including several parakeets, may be very useful for understanding the actual and potential distribution of alien species. The Ring-necked Parakeet and the Monk Parakeet are two alien species found in the Veneto region (north-east Italy) that are well-suited for conducting potential distribution studies to identify suitable areas of occurrence. In this paper, I use the MAXENT algorithm to predict the potential distribution maps of these species in the Veneto region, which finds the probability distribution of maximum entropy that is constrained by the ecological parameters considered. The authors of the Veneto photo-sound atlas kindly provided presence data for the two species. The potential distribution models for the two parakeets performed very well overall (AUC = 0.966 for Ring-necked Parakeet and AUC = 0.987 for Monk Parakeet) and indicated that high suitability areas correspond primarily to areas near known occurrences of the species. Overall, the study found that the presence of the species in provinces other than those with large populations is highly unlikely. The distribution maps produced can aid in the selection of monitoring areas for these two alien species’ populations and potential expansion.

Rescue data as an alternative for assessing trends and phenological changes in two invasive parakeet species

Monitoring population trends of alien species is pivotal to design effective management plans to preserve native biodiversity, particularly urban areas, where most populations of alien birds are established. Urban wildlife rescue centers, with personnel trained to record species, age and sex of each individual brought by the public, may represent a reliable citizen-science based method to estimate both local changes in alien species phenology and population trends. In this work, we analysed records of monk and ring-necked parakeets by comparing rescue records in the urban area of Rome from the last 15 years. We also tested whether breeding phenology of alien parakeets showed any changes since the start of the invasion processes.

We recorded a strong correlation between the number of rescued parakeets and their population trends, thus confirming the importance of wildlife rescue centers in monitoring populations of alien species in urban areas. We also observed a shift in the breeding phenology of these parakeet species. The hatching peak for ring-necked parakeet occurred in early spring, in line with previous studies on the reproduction of this species, but with a slight increase in the number of months with evidence of breeding in the last years. As to the monk parakeet, our findings support the expansion of its reproductive season between 2006 and 2020 in Rome, with chicks currently being observed for seven months a year. Therefore, data collected through wildlife rescue centers may help improving models of population growth of alien species established in urban areas.

Nesting innovations allow population growth in an invasive population of rose-ringed parakeets

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.