BY Wendy Perkins
Photography by SDZG
Videography by Victor Schwanke
When many people picture a parrot, it is usually perched in a tropical tree with a balmy breeze gently ruffling its feathers. While most people imagine that all parrot species live in warm habitats, some do live in temperate climates. Thick-billed parrots are one such bird. They prefer higher elevations and make their home in the pine forests of northern Mexico.
Cloaked in eye-catching plumage—a bright green body with crimson on the head and shoulder—thick-billed parrots live in high-elevation temperate conifer forests. They were once found from Venezuela to the southern areas of Arizona and New Mexico. Today, thick-billed parrots are found only in the Sierra Madre Occidental Mountains of northern Mexico. Estimates suggest there are just 3,000 to 6,000 left in the wild, with fewer than 1,000 breeding pairs.
The decline of the thick-billed parrot began in the 1900s, when they were heavily hunted by miners, farmers, and others; logging cleared their pine forest habitat; and the illegal capture of the birds for the pet trade increased the natural pressures of disease and predation.
The thick-billed parrot’s habitat is furnished with a variety of pine, fir, and oak trees. Pines are especially vital to the survival of these birds; the seeds make up the bulk of their diet.
Watching a thick-billed parrot eat is quite a sight. The bird clings to the large cone (some are as big as the bird itself!) and sets to work, ripping off scale after scale to free each seed. After cracking open the hard nut, the bird uses its tongue to deftly separate seed from shell. It’s a complicated process that adult birds must teach to their offspring—and it can take several months for the youngsters to get the hang of it!
Part of the Flock
For many years, thick-billed parrots were rarely kept in zoos, and had never been bred in managed care until a pair produced a chick at the San Diego Zoo in 1965. It was a proud moment for our zoo, and one that had come after years of making adjustments to diet and nest sites, in order to learn just what these loud but elusive birds needed to thrive. “We’ve been involved with this species for decades,” said Michael Mace, curator of birds at the San Diego Zoo Safari Park, “from helping with a release attempt in the 1980s (the birds had been confiscated from smugglers) to the current in situ efforts in Mexico.”
Today, San Diego Zoo Global participates in the Association of Zoos and Aquariums (AZA) Species Survival Plan (SSP) program for thick-billed parrots and works with partners to help the birds in their native habitat. “One goal of the SSP is to get to a point where there is enough genetic diversity for a self-sustaining population for 100 years,” Michael explained.
Visitors to the Safari Park can see this effort in action at Condor Ridge. In a shady aviary that mimics their forest habitat, a family of thick-billed parrots groom one another, then swoop around the aviary talking to each other in their characteristic squeaky squawk. One of their calls sounds like a deep chuckle. With their noisy habits and colorful covering, they easily charm and delight everyone who hears or sees them—usually the former happens first.
Jenna Duarte, a keeper at the Safari Park, shared an experience she had with this species in Mexico. She had traveled as part of a San Diego Zoo Global team to help with health assessments of wild thick-billed parrots. “The first day, we got out of our vehicle, and the forest was filled with their calls. We knew they were right there, but we couldn’t see them,” she said. “But we were able to record their sound. It really gives you goosebumps to hear and see them in the wild!” Michael knows how powerful this kind of experience is: “It’s a great opportunity for our staff to work in range country with species that they also care for in our collection.”
For nearly 10 years, San Diego Zoo Global has been working with Pronatura Noreste A.C., a non-governmental conservation organization that monitors thick-billed parrot nesting activity and their use of forest resources. These data help to understand how the parrots use the forest. The information is used by the local people to help determine where legal logging should be done. Our veterinary staff is spearheading a program focused on the health of thick-billed parrots in the wild. We go into the forest with our partners who are monitoring the nests and we conduct chick health evaluations. Nadine Lamberski, DVM, corporate director of animal health for San Diego Zoo Global, has led the effort, establishing health assessment protocols and implementing them in the field during yearly trips during the summer breeding season. Last summer, Jenna, who has a great deal of parrot-handling experience, joined the expedition.
“While the adult birds were out feeding during the day, we carefully handled the chicks to get weights, check for ectoparasites, and determine overall health level,” she said. “Happily, they were all healthy with no parasites!” In order to assess the adults, however, the team worked in the wee hours of the morning. The Mexican field team collected adult birds and brought them back to the campsite. After examination, the birds were released at dawn.
In addition to overall body condition, weight, and ectoparasite check, a blood draw was done on each bird. The samples are tested for West Nile Virus (WNV) antibodies, in order to determine if the birds are facing this disease challenge. Nadine explains that one of the questions the team is asking is whether and how disease is affecting the population. These birds live at higher, cooler elevations that aren’t prime habitat for WNV-carrying mosquitoes,” Nadine said. “But as temperatures rise as a result of climate change, the risk of infection in thick-billed parrots may increase. Eight years ago, there was no indication of WNV activity in the area; I’m hoping to capture when it does enter the population.”
There is cause for concern; a recent study that trapped mosquitos at various elevations did find WNV-carrying mosquitoes at 8,000 feet, within the range of nesting thick-billed parrots. “However,” Nadine said, “we’ve learned from the California condor program that we can vaccinate wild birds. So rather than predicting the demise of thick-billed parrots to WNV, we may be able to intervene and help the population.”
Thick-billed parrots are highly social. They not only feed together, they nest in close proximity to one another. A single tree might have three or more nest cavities. They prefer large-diameter trees or snags. “They not only need room for the whole family,” said Nadine, “they depend on bigger, older trees that are thick enough to insulate them from the cold—they nest in the forest at 7,000 to 9,000 feet in elevation.”
The need for old-growth trees is a challenge for the future of this species—99 percent of suitable trees have been lost to illegal logging. Artificial nest cavities have been tried—to help make up for the loss—but few birds use them. Protecting the remaining breeding forest is a key issue. Another team from the San Diego Zoo Institute for Conservation Research is hoping to help with that. This will yield valuable information on how the birds use their habitat during the nesting season, as well as monitoring climate conditions.