Arxiu d'etiquetes: accidental introduction

Invasive species. A threat to biodiversity.

If you are thinking of giving an animal as a pet, be responsible: an animal is not a toy. In addition, you have to keep in mind that many animals that we find in the stores and that are called exotic species, may in the long term pose a great environmental problem, so think about it because you are sure to find other alternatives in your gifts. In this article I will tell you what damage these animals can cause in our fauna, in particular, exotic birds, when they stop being “pets” to become “invasive species“.


Invasive alien species (IAS) are one of the main causes of biodiversity loss in the world. An exotic invasive species is one that is outside its natural range, past or present, thus assuming some kind of human intervention that translates into its transfer through a biogeographic barrier that otherwise could not have been overcome . The introduction of exotic species has been carried out for many years both voluntarily and accidentally, many from the pet trade. The problem arises when some of these species establish, reproduce successfully and disperse from the introduction zone causing true pests.

Some of these species are especially known for the economic damages they generate, such as the zebra mussel in the Lower Ebro in Spain (2 million euros per year). But they also pose a threat to our biodiversity, because of the impacts they cause on native or indigenous species (species that are within their natural range, past or present, or within their potential dispersal area, that is, to which it can reach by its own means) by competition, predation, hybridization, introduction of diseases and parasites.


As we have seen, invasive alien species have only managed to occupy areas outside their natural distribution through human intervention. Depending on the intentionality of this intervention, the introduction can be of three types:

  • Intent or deliberate: when the introduction of the species into the natural environment is premeditated, for use in biological production systems, or for recreational purposes.
  • Accidental: Occurs when there is escape or release of the animal that was kept in captivity.
  • Involuntary or accidental: inadvertent introduction of species through means of transport or communication.

When an exotic species is released into the natural environment, different stages take place (introduction, establishment and expansion) until it finally becomes an invasive species and represents a real risk.

In the case of birds, the introduction of these species is usually due to releases from individuals who have been held captive, mostly from the purchase in pet stores.

Picture 1: Argentine parrot (Myiopssita monachus) in captivity – Photo:


The Argentine or gray parrots (Myiopsitta monachus) originally inhabited forests, shrub steppes, savannahs, cultivated areas, parks and cities in south-central South America: Argentina, Paraguay, Uruguay, Bolivia and Brazil. It is appreciated as a pet, so it has been marketed worldwide, managing to escape and adapt to new areas, becoming an invasive species that causes huge problems in countries around the world. It is currently present in asilvestrada in North America, Europe and Asia.

Picture 2: Distribution map of the Argentine parrot – Photo:

It has been demonstrated that the sounds emitted by these birds have negatively affected the reproduction of insectivorous passeriformes, because they interfere in their pre-nuptial communication and in their reproduction habitat, being displaced by the parrots. Also magpies (Pica pica) have been affected due to the pressure exerted directly on them, displacing them physically, and indirectly, competing for resources. In addition, they cause significant damage to trees and crops, such as almonds (Prunus dulcis), which have seen damage during flowering and then immature almonds. According to SEOBirdLife, the spanish population of this species is estimated at about 20,000 individuals.

Picture 3: Group of argentine parrots established as invasive species in a city park – Photo:

A similar situation has occurred with the Kramer parrot (Psittacula krameri), estimating its populations in Spain in 3,000 individuals.

The common coral beak (Estrilda astrild), from South Africa; Or the black swan (Cygnus atratus) are also examples of species that were transported to our country to be kept in captivity and eventually ended up being introduced accidentally.


Species such as the wild pigeon (Columba livia) and sparrow (Passer domesticus) are invasive species in America and pose a major problem in the continent’s Biosphere Reserves, especially in Argentina, where these species are displacing native species in environments Urbanized or in the process of urbanization. On the other hand, reserves located in insular ecosystems are especially sensitive and both their integrity and their endemic species (a species or taxon originating in a determined and limited geographic area, which is only present in that area) are threatened by an abundant community of invasive species. To control the situation, management and eradication programs are maintained, however, prevention is a fundamental pillar in the control of these populations.


There are numerous global and regional initiatives for information and management on invasive alien species, including the Global Invasive Species Program (GISP), the IUCN-ISSG Invasive Alien Species Specialist Group (IUCN-ISSG), the Global Information Network on Invasive Alien Species (GISIN) and the Global Invasive Species Program of The Nature Conservancy (TNC-GISI), among others.

The prevention strategy is fundamental to minimizing the impact of invasive species and is based in full on the guiding principles of the Convention on Biological Diversity (CBD, 2002), reaffirmed in the European Strategy on Invasive Alien Species (Genovesi & Shine, 2004) , Adopted by the Standing Committee of the Berne Convention in December 2003.

The key elements taken into account in the invasive species prevention strategy are:

  • Prediction of the invasive potential of an alien species requires knowledge and assessment of a broad spectrum of variables dependent on the species’, vector and host ecosystem’s biological characteristics that may affect its establishment, impact.
  • A hierarchical approach in three stages: first, to prevent the entry of the invasive species (exclusion), to detect it quickly and eradicate it upon entry (early detection and rapid response, and finally to minimize its impact if eradication fails).

On a personal level, you can contribute to prevention taking into account some Good Practices:

  • If you observe an animal with similar characteristics to the invasive alien species in a new area, you must communicate it as soon as possible.
  • When traveling to another country, do not transport animals, plants or seeds.
  • If you are thinking of buying a pet of exotic origin do it in specialized stores. It is necessary to obtain the documents proving that the copies are duly certified, legally imported and free of parasites and diseases.
  • Collect and demand information about your pet: From what geographical area does it come? In what type of habitat do you live in your place of origin? What do you eat and how do you behave in freedom? What is its scientific name? This information will help you take better care of it and indirectly protect the natural environment around you.
  • Do not ever abandon it or release it in nature.


  • Biological invasions. Collection Dissemination of the Higher Council of Scientific Research.
  • Exotic Invasive Species. The response of the European Union. Environment, 2004.
  • Legislation on Exotic Birds. Group of Exotic Birds SEO / BirdLife, 2012.
  • Photo cover:

Sara de la Rosa Ruiz