Part 2 of 2. (Photo: Monk parakeets nest atop the entryway to Green-Wood Cemetery in Brooklyn, N.Y. Credit: Ali Cherkis)
continuing from a previous article...
In Barcelona, the birds cause more types of damage. One of Senar's studies found that in an agricultural area outside the city, parrots caused a loss of 28 percent of the corn crop, 36 percent of the plum crop and 37 percent of the pear crop, among other fruits and vegetables grown there. They also clip many branches from live trees for their nests and eat food that other, native species rely on.
Senar emphasizes that he loves the species—he enjoys watching them and makes a living studying them. But there's a difference between enjoying a few parakeets and dealing with thousands of them roaming the city. He fears they'll soon harm ecosystems beyond the city limits if their population isn't managed: “They're very clever. If we wait too long, it will be nearly impossible to control them.”
Another, equally adorable parrot species, the Rose-ringed Parakeet (also known as the Ring-necked Parakeet), illustrates how difficult it can be to control these charismatic birds when they set up shop outside their normal range. Like the Monk Parakeet, this species is successful in its native home ranges in South Asia and sub-Saharan Africa, where it can thrive in human-altered habitats. A popular caged bird since at least Victorian times, the green, pink-beaked, long-tailed parrot started escaping increasingly often in the past few decades; before long the Rose-ringed Parakeet established itself in cities across Eurasia and beyond. But unlike Monk Parakeets, Rose-ringed Parakeets don't build their own nests. They rely on nest cavities, a limited resource for native wildlife—and they aren't afraid to fight for those spaces.
As the species began colonizing cities, scientists organized to understand the birds and their impact. In 2013 the European Cooperation in Science and Technology funded ParrotNet, a five-year project, headquartered at the University of Kent in England, involving a network of scientists across Europe tasked with monitoring parrots and communicating their findings to local governments.
Emiliano Mori, a researcher at the Italian National Research Council and former ParrotNet member, first noticed the birds on a Mediterranean summer holiday and wondered how they were affecting the native biodiversity. He began observing the parrots and the outcomes of their invasion. Soon he found that Rose-rings were taking nest sites from a small owl called the Eurasian Scops Owl in Italy. The species wasn't directly reducing the owls' population, but it was pushing them out of their preferred spots.
Evidence of the negative consequences of Rose-ringed Parakeets' entry into new locales continues to mount. Research has shown that they outcompete birds at feeding stations in the U.K., and they regularly kill competitors such as Blue Tits and black rats. All the while their populations have been ballooning in cities around the world.
“Their presence is not good,” Mori says. “We can't tell the complete scope of their impacts, but every time we look, there's something new to be discovered.” The researchers continue to find new species affected by the birds, he says.
ParrotNet produced policy briefs that were translated into various European languages. Spain has begun removing parakeets. But culling programs are running up against humans' enduring fascination with these birds.
Green-Wood Cemetery's Monk Parakeets and other urban parrots are by-products of the pet trade and wildlife trafficking. Credit: Ali Cherkis
The parrots' cute factor continues to be a challenge in efforts to control them, says biologist C. Jane Anderson, who specialized in charismatic invasive species while she was an assistant professor at Texas A&M University Kingsville. Anderson studied Rose-ringed Parakeets on the Hawaiian island of Kauai, where the birds threaten local agriculture and native species. She used culled samples to determine when the birds bred and how to tell the difference between juvenile and adult females—they look similar, but removing (and euthanizing) the latter is more important for population control.
Anderson can recall multiple anecdotes of public protest hindering invasive-parrot management. Humans are drawn to animals with babylike features, called “baby schema ” in psychology: big eyes, big heads and soft bodies. Culling snakes might not lead to much outcry, but people like parrots.
It's important to remember how the birds arrived in the first place, Anderson says. She doesn't want to demonize the parrots; rather she views controlling them as undoing the damage humans caused. “The truth is humans moved these animals around,” she says. “I understand why people would be excited to see a parrot in Barcelona. But they shouldn't be there.”
It's also important to understand that our cities are not sterile places devoid of wildlife that needs protection. Cities can be as ecologically valuable as the surrounding countryside—New York City is a major migratory bird hotspot, for example. Perhaps the most worrisome consequence of the Rose-ringed Parakeets is that they outcompete and kill a type of threatened bat called the greater noctule at the site of their largest known colony in Europe—an urban park in the Spanish city of Seville.
The paradoxical truth of the matter is that cities can also serve as vital habitat for some parrot species. Australian cities host several native parrots, including the Sulphur-crested Cockatoo. This big, white parrot, named for its sleek yellow mohawk, is a regular sight around gardens in Melbourne, Brisbane, Sydney, and beyond. Although their population is in decline overall, they're not listed as threatened, and they have found a way to survive successfully in cities. They've inhabited urban spaces as long as there have been urban spaces, says Lucy Aplin of the Max Planck Institute of Animal Behavior in Radolfzell, Germany, and the Australian National University. “Parrots have the potential, if given the opportunity, to exhibit rapid adaptation to anthropogenic change.”
In contrast to Monk and Rose-ringed Parakeets, which start breeding between the ages of one and three years and lay at least three eggs at a time, Sulphur-crested Cockatoos don't generally breed until they're at least three or four years old, and they lay just two to three eggs per nesting season. They're particular about where they nest, seeking out large cavities in old trees. Yet they've been able to thrive in Australia's major metropolitan areas.
Certain traits of Sulphur-crested Cockatoos make them quite well suited to city life. For one thing, they are generalists, feeding on whatever food they can find—fruits, invertebrates or a discarded chicken bone. And they're highly intelligent, social creatures capable of solving problems and teaching their solutions to others. These birds can build a culture around urban living, passing knowledge through social networks like humans do. Aplin studies a behavior that has emerged in Sydney's Sulphur-crested Cockatoos: they've figured out how to open garbage bins. A group of the birds in southern Sydney first learned to open the bins, and they transferred the knowledge to nearby cockatoo roosts. Birds outside the network don't necessarily know how to do it. Aplin's work has shown that birds on opposite sides of the network have diverged into subcultures, opening the bins in different ways.
For some imperiled parrot species, cities may be more than just another comfortable place to call home—they can be a lifeline. Parrots whose native populations are threatened with extinction are holding on in some of the world's largest cities. Consider Hong Kong's Yellow-crested Cockatoos.
During the 1980s and into the 1990s, pet traders exported tens of thousands of Yellow-crested Cockatoos from their native Indonesia to Hong Kong, says Astrid Alex Andersson, a postdoctoral researcher at the University of Hong Kong. Enough birds escaped captivity or were intentionally released by their owners that they founded a colony in the city. Although much of Hong Kong is forested, these birds prefer to nest and feed in the ornamental trees found in the island's urban areas and don't seem to be outcompeting any native species.
About 200 Yellow-crested Cockatoos live in Hong Kong—approximately 10 percent of the bird's remaining population, says Caroline Dingle of the University of Hong Kong. Population decline from poaching pressure in its native habitat led the International Union for Conservation of Nature to designate the species as critically endangered. Andersson is studying whether the species has found a useful refuge in the city, where it's not subject to poaching pressure. “It's possible that these populations, if you do small things to support them in cities, can function as species arks—backup populations for the wild ones,” she says.
Credit: Ali Cherkis
Nevertheless, city living isn't all great for parrots. There's predation: Mori says feral Rose-ringed Parakeets regularly become prey for raptors, for example. Even for the endangered Yellow-crested Cockatoo, it'll take further work to determine whether the Hong Kong populations can actually function as a genetic reservoir or whether city life has altered them too much to sustain the species. As part of her research, Andersson is investigating how the city cockatoos differ genetically from the native population.
A similar question preoccupies Smith-Vidaurre. In the U.S., she is looking at the complex vocalizations of Monk Parakeets and how they differ between native and introduced individuals. Each parrot has its own distinctive voice with changes in the frequency of its squawks. She found that the introduced parrots have less complex calls than birds in the native ranges. “Something about their environment might be constraining their ability to produce or perceive these vocal signatures,” she says. How permanent are the changes, she wonders? Would an introduced parrot be able to return to its native range and thrive?
For better, for worse, and sometimes both, parrots have taken over our cities. Their ability to thrive in our altered habitats is a testament to what makes these species special and why we should work to conserve them in the wild while minding the potential impacts of introduced parrots. They're innovators, problem solvers, socializers and survivors. That's how they earned our adoration in the first place. Sometimes it's a joy to stop and marvel at the parrots.
Ren Ecosystem