Anyone walking around Barcelona can easily see small and noisy birds with greenish plumage, with the breast part of a more grayish color. Looking down, you can see their signatures in the form of excrement and, looking up, surprise us with their gigantic nests. This is the Argentine parakeet (Myiopsitta monachus). In less than 50 years these seemingly harmless birds, which arrived as pets, have taken over the city.
The last official census put the numbers in Barcelona at just over 5,000. However, scientific estimates ensure that this number has now doubled, reaching around 10,000 in the Catalan capital alone. If the population of the metropolitan area is added, the figure would be close to 20,000, according to experts such as Joan Carles Senar, head of research and scientific publications at the Natural Sciences Museum of Barcelona.
The exponential growth of the Argentine parakeet in the Catalan capital is due to several factors. One is its high reproduction rate. It is estimated that in the Catalan capital it doubles what they have in their native areas, especially Argentina and Uruguay. “The population of this species doubles every eight years”, highlights Senar.
Beyond its reproductive success, its resistance to diseases such as the Newcastle virus is also remarkable. Senar points out that, despite the fact that around 30% of parrots are carriers of this parasite, it does not affect them. Added to this is the lack of predators and the low genetic variability of the specimens present in Europe and the United States. “It seems that there has been a selection that has favored a series of stronger individuals”, points out the expert.
The presence of the Argentine parakeet, despite its colorful and friendly appearance, is not at all positive for the ecosystem, as it is described as an “invasive exotic species”. In other words, it is “an agent of change and a threat to native biological diversity, either because of invasive behavior or because of the risk of genetic contamination”, as specified in Royal Decree 630/2013.
One thing that makes Argentine parakeets different from other types of parrots is that it is the only animal in this family that builds its nests using branches, as Senar explains. “This gives them much more independence”, he adds. This ability to adapt allows them to build nests in all kinds of trees, especially palms and pines, and also in structures such as light poles. In addition, Argentine parakeets are very social animals, they breed in colonies and usually live as a family in the same nest. For this reason, they can be very large and have dozens of offspring. Consequently, the nests can become very heavy, exceeding 100 kilos and have a high risk of falling. To avoid this, withdrawals are made from the nests at risk of succumbing. In the first three months of 2023, for example, municipal sources indicate that 176 nests have already been removed, also coinciding with the winter pruning season. In addition, the City Council, through the Municipal Institute of Parks and Gardens, awarded a new contract in January to a specialized company to remove nests at risk of falling during the breeding period. The document foresees the withdrawal of 390 per year.
Another of the big problems that parrots represent wherever they settle is the damage they cause to the surroundings. This is because these birds collect branches to make their nests, but also because they eat everything around them, such as fruits, flowers or leaves. “Their population increase requires more food, and this threatens to leave other bird species with fewer products to feed on,” explains Senar.
Measures must be taken to achieve population control or, ideally, eradication. At the same time, it is important to make the population aware of this need. “To achieve this, the public must be informed”, explains Senar. And it seems that it is being achieved. According to a recent survey by the Natural Sciences Museum of Barcelona and the Public Health Agency, there are currently 11% more people in favor of population control than 15 years ago. However, the expert explains that there are still many undecideds. Another remarkable fact is that in this same period there has been a 22% increase in people directly affected, in different ways, by the presence of Argentine parrots.
The method used to achieve this control in any case must balance effectiveness and social approval. Those that could be more widely accepted, such as the use of contraceptives, would be ineffective for a species with these biological and reproductive characteristics. Senar proposes the capture of specimens in the nests and the subsequent ethical sacrifice. With this method, he says, the population could be eradicated in about a decade. What is clear is that “the city cannot be a large cage of domestic animals that keep expanding”.
