In the parks and gardens of some cities in Spain and Europe we have serious problems, caused by the invasion of two species of parrots, which were originally introduced as pets. One is Kramer’s Parrot ( Psittacula krameri ), a highly invasive species from Africa and South Asia. The other, the Argentine parrot ( Myiopsitta monachus ) , also invasive, from South America. Both species generate a series of impacts on the ecosystems they invade, although each affects them in a different way.
Parrot Impacts
Among the damage caused by the Kramer ‘s parrot, the great impact on the local fauna stands out. It is a species that nests in holes in trees , a resource for which it competes against other birds and bats. In fact, Kramer’s parrot is causing the giant noctule, a threatened bat, to run out of nesting sites.
In a study carried out by Dailos Hernández-Brito, from the Doñana Biological Station, it is highlighted that in less than 15 years the occupation of these holes by Kramer’s parrots multiplied by 20, while the number of trees occupied by bats decreased by more than 80%. It also competes for other resources such as food, changing the habits of native fauna, such as sparrows or woodpeckers. Ironically, it is the latter that usually make new holes in the trees, where, after abandoning them, other species nest, so their disappearance turns these holes into a limiting resource.
On the other hand, we have the Argentine parrot . Unlike the previous one, this one makes the nests and does not occupy holes. In addition, the huge nests represent a new impact: it is an ecosystem architect species, that is, it changes the structure of habitats. Its heavy weight can cause damage to trees or structures where it is installed. Serious damage to electrical infrastructure has been reported. On the other hand, these parrots have been shown to cause serious impacts on agriculture, particularly cereal. In some fields near cities invaded by the Argentine parrot, up to 98.6% of the reported damage to crops is attributed to this animal, which is considered a pest.
In both cases, noise pollution must be added, which can influence the habits of the local fauna and the health of people. And in this regard, it is worth highlighting another potential impact that may be worrying. Parrots can be a reservoir for a pathogen called Chlamydiophila psittaci, the causative agent of human psittacosis.
Feasibility, efficacy and specificity
Any method that we try to manage the invasion by parrots must meet three essential requirements: viability, that is, that it can be carried out; effectiveness, that is, achieving successful results; and specificity , that is, that it affects only the species that we want to control, without affecting other animals.
One of the measures that turned out to be the most popular a few years ago was the use of sterilizing feed . Without a doubt, placing feeders with this type of product available to the parrots is viable; they are easy to handle, and their use can be extended over time. However, it does not meet the other two requirements. It is not effective, since animals rarely consume the necessary dose to be sterilized, on the contrary, it makes their lives easier, because after all, these feeds are an extra supply of food. And finally, it is a tremendously non-specific measure that can affect other birds, sterilizing them.
One more measure of the proposals is the substitution or elimination of eggs . This measure is totally specific; you only delete the eggs you want to delete. But the incubation period for parrots is just a few weeks, and acting on thousands of eggs in that short period of time is unfeasible . In addition, it is a measure that should be done every year.
The option of capturing the animals, sterilizing them and setting them free was then raised. But the parrots are intelligent animals that quickly learn to avoid traps, so the measure requires changing the trapping method from time to time; Added to the enormous number of parrots in some Spanish cities, it makes it an unfeasible measure . Not counting the veterinary costs involved in sterilizing thousands of animals.
In addition, the measures that imply that the parrots are released, there is an additional problem that makes all of them ineffective. Parrots, even sterile and without eggs, are very long-lived and will continue to cause impacts for decades. Also, releasing them again is illegal.
As a possible solution to this problem , the integration of animals in specialized centers has also been proposed ; this can be used for places where there are very small populations of parrots. But in large cities it is unfeasible, not only because of the difficulty of capturing it, but also because there is currently no infrastructure capable of housing and maintaining such a large number of animals without risk of escape.
Finally, sending parrots back to their native region is also not possible . Not only because of the already raised difficulty of capturing all these animals, but also because, in addition, the invasive population has suffered a powerful selective effect in the form of a bottleneck, causing it to have very little genetic variability and to be very competitive animals, significantly different from the original native population. The reintroduction would be to move the ecological disaster to another site , and the native population of parrots would be in serious danger.
Without forgetting that all the systems that involve the transport of these animals, and even more so, veterinary interventions, entail stress and suffering for the animals.
Of all the systems that we know to eliminate the invasion by parrots, the only one that, so far, has been really viable, effective and specific has been selective control with a compressed air rifle. It is, as far as we know, the method that entails the least unnecessary suffering for the animal, since death is almost instantaneous.
Of course, the best solution that exists to this type of problem is prevention. Avoiding introducing exotic species is the optimal way to prevent them from becoming invasive. And when they are already present, establishing early detection and rapid response systems is the most effective way to control populations that are still small, before their management becomes a problem, not only economic, but also among public opinion. However, when all these measures are late, it is necessary to act as soon as possible; the later, the more difficult it will be to tackle the problem.
REFERENCES:
Postigo Sánchez, JL 2021. Scientific analysis of the situation of the parrot in Madrid and in Spain, management alternatives and denial of hoaxes about parrots. EFE Green November 26. https://www.efeverde.com/blog/creadoresdeopinion/analisis-cientifico-sobre-la-situacion-de-la-cotorra-en-madrid-y-en-espana-alternativas-de-gestion-y-denial- de-hoaxes-about-the-parrots/
Castro, J., Sáez, C., et al. 2021. The monk parakeet (Myiopsitta monachus) as a potential pest for agriculture in the Mediterranean basin. Biological Invasions. DOI: 10.1007/s10530-021-02702-5
Hernández-Brito, D., Carrete, M., et al. 2018. Nest-site competition and killing by invasive parakeets cause the decline of a threatened bat population. Royal Society Open Science, 5(5), 172477. DOI: 10.1098/rsos.172477
Menchetti, M., & Mori, E. 2014. Worldwide impact of alien parrots (Aves Psittaciformes) on native biodiversity and environment: a review. Ethology Ecology & Evolution, 26(2-3), 172-194. DOI: 10.1080/03949370.2014.905981
Roy, H. E., European Commission, et al. 2015. Invasive alien species: prioritising prevention efforts through horizon scanning: final report. Publications Office. http://dx.publications.europa.eu/0.2779/096586
Saavedra, S., & Medina, F. M. 2020. Control of invasive ring-necked parakeet (Psittacula krameri) in an island Biosphere Reserve (La Palma, Canary Islands): combining methods and social engagement. Biological Invasions, 22(12), 3653-3667. DOI: 10.1007/s10530-020-02351-0
