Changing soundscapes. The spread of parakeets in Europe

This is going to be another “noisy spring”. The melodious notes of native black birds, wrens and robins are being progressively replaced in many European towns by the frequent loud screeching calls of monk parakeets and rose ringed parakeets. The genuine “soundscape” of European towns is indeed rapidly changing, replaced by the exotic calls of parakeets, which are becoming a familiar sound in many European cities, particularly in urban areas and parklands. Roosting sites are sometimes spectacular, as they may often contain several hundred birds attracted from a wide area to just a few trees. Nevertheless the screeching calls of parakeets in Europe, rather than being considered a mere novel fascinating thing, should remind us of the actual and potential threats they represent. In the old continent parakeets are not native species, as they have created breeding colonies only recently, further to intentional releases or accidental escapes of animals traded at least since the 60's as cage birds. Like many other invasive alien species, their presence can be detrimental to the environment and human welfare.

Monk parakeet (Myiopsitta monachus) in a cage
© Photo: Riccardo Scalera

Take for example the rose-ringed parakeets. This native to the African continent south of the Sahara and to south Asia, is now the most widely introduced parrot in the world (including at least 12 countries in Europe). In Europe, besides being a clear noise nuisance as already considered in some residential areas, can have a major impact on biodiversity, agriculture and even health. In fact rose-ringed parakeets may have detrimental effects on native birds with which they may compete, particularly in those habitats where the number of cavities as breeding sites is a limiting factor regulating population densities of cavity-nesters (e.g. for species like Eurasian nuthatch,  kestrel, stock dove, western jackdaw and common starling). 

In Europe most rose-ringed parakeet populations were initially introduced in urban environments, thus the impact on agriculture has been historically limited. However, they are now extending their range into rural environments, thus increasing the potential to become agricultural pests. Although the reports of parakeet damage to agriculture are still few, there is clear evidence of significant damage to crops as well. For example, in the United Kingdom rose-ringed parakeets damage buds and blossoms of various trees and shrubs. For this reason conflicts are known with fruit growers that experienced damage to apple, pear, cherries and plums. In addition, this parakeet has been reported to have damaged vineyards by reducing the expected wine production. Also in Australia, where the species is not native, rose-ringed parakeets are known to cause severe damage to plantations by stripping the bark from young stems and killing the affected trees, thus locally changing the arboreal composition. On the other hand, in at least part of its native range this species is considered one of the most destructive bird pests for agriculture. In India and Pakistan, for example, there are extensive reports of crop damage. 

Rose-ringed parakeet eating plums in Versailles
(Psittacula krameri)  © Photo: Riccardo Scalera

Rose-ringed parakeets are also possible vectors for diseases, like Newcastle's disease and cryptosporidium, which could be harmful to poultry and might also have an impact on that industry. Moreover, they could affect humans in the case of psittacosis. In any case, the potential for the parakeets to become serious pests in the future has been highlighted, in fact there is concern that farming practices that adapt to global climate change and a warmer Europe will facilitate the continued expansion of parakeet populations. As a consequence, given the detrimental impacts of parakeets occurring outside their natural range, it would be useful to monitor existing wild and captive populations, and to improve legislation to prevent deliberate introductions and escapes. Moreover, depending on the risks posed, population control or eradication may be considered necessary to limit the spread of the species and the potential for further damage. But this might be not very popular. The experience with the monk parakeet control in London (described here) is a good example of the challenges and opportunities of this option in Europe, with a special focus on the social dimension of the problem represented by this South American parakeet.

A dedicated EU project – ParrotNet - is just being launched with the aim to create a European network focusing on the impacts, drivers and monitoring of invasive parrots in Europe, and promoting the understanding of relevant invasion dynamics and risks to agriculture and society. ParrotNet is a COST Action, led by the University of Kent, UK, and will provide funding for a 4-year research network (for further information see here). The project, comprising currently 14 European countries, will help to (i) better understand why some species such as parakeets are highly successful invaders, (ii) harmonise methodologies to predict agricultural, economic, societal and ecological impacts across Europe, and the means to mitigate them, (iii) create a virtual European Monitoring Centre for all invasive parrot species, and (iv) transfer results to policy and society.  This is a key attempt to prevent that Carson's prophesy of a “silent spring” will be replaced in the near future by a more and more insidious “noisy spring”.

Does this snail look sufficiently "alien"?

The European Commission has recently issued a decision according to which the so called apple snails shall not be imported into or spread within the European Union (see Implementing Decision of 8 November 2012).

The new legal provision targets any organisms of the genus Pomacea, and regulates the introduction into and the movement within the region of all plants that might represent an effective pathway for such freshwater snails e.g. all plant species for planting that can only grow in water or soil that is permanently saturated with water.

Apple snail Pomacea canaliculata © Riccardo Scalera 

The apple snails are mollusks characterised by a very large shell, which may reach the size of an apple as the name suggests. They are native to South America and have been introduced in many countries of the world, particularly in North America and Asia, both intentionally or accidentally as a consequence of the food and the aquarium trade (see for example the case of Pomacea canaliculata as reported by the GISD). In Europe the only known record of occurrence of apple snails is in Spain. 

In fact the EC decision come in response to a risk assessment analysis made by the European Food Safety Authority (EFSA) and the Spanish authorities, following the discovery of the presence of the apple snail (Pomacea insularum) in the Ebro delta, where it has been causing damage to rice production and the natural environment. According to the risk analysis (PRA), a legislative ban on import of the entire genus Pomacea was the only risk reduction option identified that could reduce the probability of entry of this potentially invasive alien species. Besides, the PRA established that: a) the potential consequences of the organism for rice crops are major; b) the probability for establishment of the organism is very likely and c) the probability of spread is estimated as likely. Thus, while rice fields and natural wetlands are known to be at risk, many other aquatic environments could also be threatened, due to the snail's voracious appetite for water plants and the fact that it can survive in a wide range of climatic conditions.

The objective of the legal provision is to prevent the further release of the snail into the environment, either intentionally or accidentally. In fact, in the absence of less restrictive measures efficiently combating the threat posed by that organism there is a high risk of spreading of this freshwater snail to fields and watercourses, lakes, ponds and swamps. The provision does not focuses only on Pomacea insularum (the species reported in Spain) because other species might be available in the market to replace it, and in any case many other species from the complex are almost indistinguishable.

The decision also requires Member States to adapt their legislation in order to comply with the specified rules, including the establishment of demarcated areas in cases where the genus Pomacea is found to be present in fields and watercourses. In principle this should be a first step to eradicate the organisms concerned, to raise awareness as appropriate and to ensure intensive monitoring for their presence. Wherever necessary Member States should carry out annual surveys in areas where the specific organisms are likely to be found, e.g. rice fields, and notify the results accordingly (even though the presence of the snail is only suspected). In the meantime in Spain, as reported by EPPO, an action plan was implemented to control and eradicate the apple snail. The main measures included phytosanitary and disinfection treatments, removal of adults and eggs, physical barriers, and surveys.