The Invasion Dynamics of Monk Parakeets in Urban Parks

The monk parakeet (Myiopsitta monachus) is native to the subtropical and temperate woodlands of South America. Historically it was mainly distributed along woodland edges bordering the Pampas grasslands. Since the twentieth century, however, its population has expanded rapidly. Not only have its numbers increased dramatically within its native range, but through the pet trade and accidental introductions the species has established populations on several continents and become an invasive species in many regions. Its large communal nests and colonial breeding behavior frequently interfere with urban infrastructure, making the bird a subject of controversy in many cities. Yet this same nesting habit offers researchers an opportunity to examine how its nesting choices reveal ecological strategies that contribute to its invasion success.

Monk parakeet（圖片來源：Luis García (Zaqarbal)，採用 CC BY-SA 3.0 授權）

Unlike most parrots that rely on tree cavities for nesting, monk parakeets are among the few parrot species that construct massive communal nests. These structures resemble social housing complexes, typically containing multiple entrances and separate breeding chambers capable of accommodating dozens of individuals at once. Such nests provide protection against wind, rain, and predators while also facilitating social interaction and cooperation among group members. This distinctive nesting strategy may allow the species to establish itself quickly in unfamiliar environments. Instead of depending on scarce natural cavities, monk parakeets can construct nests on a wide range of tree species and even on artificial structures.

Monk parakeet nest（圖片來源：CHUCAO，採用 CC BY-SA 3.0 授權）

Monk parakeet nest（圖片來源：Enrique González，採用 CC BY 4.0 授權）

A study conducted in five major parks within Buenos Aires recorded the distribution of monk parakeet nests in relation to tree species. Among 1,758 surveyed trees, only 3.4% were used for nesting, yet those trees supported a total of 128 nests. This pattern indicates that nest placement is far from random. Rather, the birds show clear preferences for certain tree species. Atlas cedar (Cedrus atlantica) alone supported about 40% of all recorded nests, and a single tree could contain as many as sixteen nests. Other frequently used trees included several palm species within Arecaceae and members of the genus Araucaria. In contrast, although eucalyptus (Eucalyptus) trees often serve as nesting sites in rural landscapes, they were rarely used within the park environments examined in this study, suggesting that environmental context strongly influences nest tree selection.

Atlas cedar appears particularly attractive as a nesting substrate because of its structural characteristics. The species has a vertical trunk with horizontally spreading branches arranged in regular layers. Dense evergreen foliage forms numerous concealed spaces within the canopy, reducing exposure to predators and harsh weather while providing strong support for the large communal nests. Trees of the genus Araucaria share several of these structural features. Palm trees, by contrast, offer a different but equally advantageous architecture. Their smooth, upright trunks make them difficult for terrestrial predators to climb, while the umbrella-like crown of leaves at the top provides shelter for nests even when the trees themselves are relatively short. Each of these structural traits creates suitable nesting conditions for monk parakeets within the urban environment.

Monk parakeets do not restrict themselves to trees. They frequently construct nests on utility poles, telecommunications towers, and stadium lighting structures. Their flexibility in substrate use demonstrates a high level of adaptability, but it also intensifies conflicts with humans. Large nests built on electrical infrastructure can cause short circuits or even fires. The spatial distribution of resources and human activity also influences nesting locations. In parks, monk parakeets are often observed nesting near recreational areas or food stalls. Some visitors intentionally feed the birds, inadvertently supporting population growth.

Monk parakeets building nests on artificial structures（圖片來源：Greg Schechter from San Francisco, USA，採用 CC BY 2.0 授權）

Urban planning may therefore play an important role in managing monk parakeet populations. If city parks avoid planting large numbers of tree species favored for nesting, such as cedars or Araucaria, or if tree arrangements reduce structural conditions suitable for nest construction, population expansion of this invasive species could be limited. Management strategies based on ecological understanding provide a more humane alternative to traditional control methods that rely on lethal measures.

At the same time, the behavior of invasive species cannot be assumed to remain constant across environments. In rural landscapes eucalyptus trees are often preferred nesting sites, yet in Buenos Aires city parks they are seldom used. This contrast demonstrates that invasion success does not arise solely from the intrinsic traits of a species. Instead, it emerges from the interaction between those traits and the ecological conditions of a particular location. Effective management must therefore be grounded in local environmental context rather than relying on generalized assumptions.

The case of monk parakeets in Buenos Aires illustrates a broader challenge associated with urbanization and biological invasions worldwide. Urban green spaces provide valuable recreational environments for residents, yet they can also become refuges for invasive species. Balancing the preservation of urban greenery with the maintenance of ecological stability will remain a central issue for future urban ecosystem management. Monk parakeets, with their remarkable nesting strategy and adaptability, stand precisely at the intersection of these competing priorities.

Author: Shui-Ye You

Reference:

Romero IP et al. (2015). Nest Building by Monk Parakeets Myiopsitta monachus in Urban Parks in Buenos Aires, Argentina: Are Tree Species Used Randomly? BioOne.