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TWS2022: Reintroduction is boosting Puerto Rico parrot survival
Endangered birds only live in three wild populations on the island
Reintroduction efforts are critical to recovering Puerto Rico parrots—without sustained efforts to return the endemic birds to the forest, their wild populations would decline.
A million Puerto Rico parrots may once have lived in the wild on the island, but decades of deforestation meant the removal of most of the habitat for these charismatic green, blue and red birds. While they once ranged widely across the island, by the 1970s, only a single remnant population of 13 wild birds remained, occupying El Yunque National Forest. The U.S. Fish and Wildlife Service listed the parrots as endangered in 1967, prior to the passage of the Endangered Species Act.
The recovery process began in 1973. Wildlife managers with the USFWS, the U.S. Forest Service and the Puerto Rico Department of Natural and Environmental Resources began taking steps to release captive-bred Puerto Rico parrots (Amazona vittate) into the wild. They started in El Yunque in the 1980s, then added Rio Abajo State Forest in 2007. More recently, wildlife managers have begun to reintroduce a third population into Maricao State Forest. They do this both by releasing captive-bred birds and by taking chicks from aviary nests and placing them in wild parrots’ nests. They also boost wild populations by setting up nest boxes—Puerto Rico parrots nest in cavities in old, dead trees, which aren’t always easy to find in [younger forests].
Today, roughly 690 Puerto Rico parrots occur on the island—including those in captive breeding aviaries.
In research presented at The Wildlife Society’s 2022 Annual Conference in Spokane, TWS member Lisa Faust, senior director of population ecology at the Lincoln Park Zoo in Chicago, and her colleagues have analyzed the population viability of these three wild populations, as well as two populations of captive birds in aviaries used for the breeding programs.
The research revealed that all three wild populations would continue to decline without reintroduction efforts. The Rio Abajo population was the most viable—Faust’s models showed that without management, it would only decline by about 1% per year. In El Yunque, where the numbers have never topped 60 and the birds face a 31% chance of extinction, the population would drop 5% per year without management.
It isn’t clear why parrots in El Yunque struggle more than those in Rio Abajo, Faust said. The El Yunque parrots are a remnant population, and the area has the oldest intact forests, which the parrots prefer. But it also bears the brunt of most tropical storms that hit Puerto Rico, she said, and that may make it harder for them to survive.
“The forests are different there,” Faust said. “The El Yunque population, even though it’s the remnant—it had always struggled.”
While the Rio Abajo forests experience less intense storms, they remain a challenge, especially for fledgling populations. That’s also true in Maricao, where reintroduction efforts were put on hold due to hurricanes Irma and Maria in 2017. These storms also damaged the two aviaries, affecting populations there.
While Puerto Rico parrots have evolved in an environment that has always experienced hurricanes, these storms can have an outsized effect on today’s smaller populations.
“Historically, they were adapted to hurricanes, and they were able to survive and persist,” Faust said. But with small populations, “[tropical storms] can be devastating for a species.”
Climate change could create more concerns, Faust said. Her team’s modeling found that if tropical storms increase their intensity or frequency, all three populations will decrease.