Annual Censuses and Citizen Science Data Show Rapid Population Increases and Range Expansion of Invasive Rose-Ringed and Monk Parakeets in Seville, Spain.

José L. Tella,Dailos Hernández-Brito,Martina Carrete

doi:10.3390/ani12060677

Abstract

Simple SummaryMonitoring programs are crucial to understanding and managing invasive species populations. However, they are infrequent and not usually conducted in the long term. In this work, we used population censuses and observational data from citizen science platforms to monitor the growth and expansion of populations of two invasive species established in Seville (Spain): the rose-ringed parakeet and the monk parakeet. During our study period (2013–2021), rose-ringed and monk parakeet populations increased fivefold and twentyfold, respectively. These rapid population growths coincided with the increasing number of observations of both species recorded by volunteer birdwatchers, as well as the increasing expansion of monk parakeets throughout the study area. Citizen science can be useful for roughly knowing the population status of invasive species, but it cannot replace specific monitoring programs to understand their spatiotemporal dynamics.Population changes of invasive species can go unnoticed long before population explosions, so long-term monitoring programs are needed to assess changes in population size. Although invasive populations of rose-ringed (Psittacula krameri) and monk parakeets (Myiopsitta monachus) are present worldwide, their current status and dynamics are mostly poorly known. Here, we provide a long-term population monitoring of both parakeet species established in a Mediterranean urban area. Between 2013 and 2021, we conducted systematic population censuses in the city of Seville and collected their occurrence and spatial distribution data from citizen science platforms. Our censuses showed a rapid population growth of both species: rose-ringed parakeets increased from 1200 to 6300 individuals, while monk parakeets increased from 70 to 1487 individuals. These population trends were weakly reflected by the number of parakeet observations and the number of cells with parakeet observations but not by the number of individuals recorded in citizen science platforms. Moreover, for the monk parakeet, the number of cells with observations was related to the spatial spread of its nests across the study area. Although resource-intensive, long-term monitoring programs are essential to assess population changes and develop effective management actions for invasive species. Thus, contrasting this information with data taken through citizen science platforms can validate the utility of the latter for assessing population status of invasive species.

Highlights

Invasive species are among the main drivers of global change due to their ecological impacts, which can be enormous [1,2] and even irreversible, such as contributing to the extinction of native species [3,4]
Our censuses showed a rapid population growth of both species: rose-ringed parakeets increased from 1200 to 6300 individuals, while monk parakeets increased from 70 to 1487 individuals. These population trends were weakly reflected by the number of parakeet observations and the number of cells with parakeet observations but not by the number of individuals recorded in citizen science platforms
This magnitude of impacts is positively correlated with the population size of invasive species [1,5], so monitoring and studying their populations from the early stages of invasion processes are key to the understanding and management of biological invasions [6–8]

Summary

Introduction

Invasive species are among the main drivers of global change due to their ecological impacts, which can be enormous [1,2] and even irreversible, such as contributing to the extinction of native species [3,4]. Population dynamics can be complex when invasive species exhibit lag phases before population explosions [12,13], as well as when interactions between invaders, native biota and the recipient environment regulate their population growth [14,15] These factors, which may complicate both early detection and the design of effective invasive species monitoring programs, can invalidate the usefulness of citizen science data for monitoring the population trend of these species. Parrots (Order Psittaciformes) are a prime target for the pet trade, which contributes to the decline in their natural populations [17] and to the introduction of 16% of parrot species outside their native distributions [18] The origin of these introductions is the accidental or deliberate release of individuals kept in captivity that have successfully established populations in the wild [19], mainly in urban environments [20].

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