This San Francisco story begins somewhere along the coast or tropical dry forest of Ecuador or Peru, sometime before the 1980s, in a hole in a tree.
One day, wild red-masked parakeet nestlings—blush-pink, prickly with pinfeathers, and snug in their nursery in a tree—may have heard a machete thwack at the base of their tree or felt hands clasp around them. They were captured because they would mature into adorable, charismatic, dazzling birds, with lime-green bodies, scarlet heads, and clever grins. And people in the U.S. wanted adorable, charismatic, dazzling pets. So, frightened and disoriented, and likely forced into a box crowded with other birds, the nestlings entered the pet trade. They were sold as “cherry-headed conures.”
In 1988, a few appeared in the urban wild of San Francisco. It’s not clear how they got there; it’s also not hard to guess. These medium-size parrots are hot-headed and loud-mouthed. Maybe they escaped, or maybe a tired owner tossed a maelstrom of squawking feathers out a window. Either way, they were free in the City by the Bay.
Genomic research now reveals details of their story. Dara Torgerson and Jacqueline Robinson, then both researchers at the University of California, San Francisco, partnered with Stanford University and Mickaboo Companion Bird Rescue to produce the first complete genome of a San Francisco red-masked parakeet (Psittacara erythrogenys) and then compare it with genomes from birds inside and outside the flock.
The San Francisco birds weren’t all red-masked parakeets, as it turned out. Instead, the researchers found, they were hybrids of red-masked and mitred parakeets (Psittacara mitratus)—a species that looks almost the same but hails from a totally different region of South America. The genome reveals a human-created flock, trying to find success in a human-manipulated habitat. “They’re their own thing now,” Robinson says.”
How an angry conure helped science
Torgerson, an evolutionary population geneticist, primarily studies humans and flies, but her passion is parrots. As a Mickaboo volunteer, she also helps care for and fosters injured San Francisco flock members, many of which suffer neurological damage from ingesting the rodenticide bromethalin.
That’s how she met Acorn. A wild San Francisco parrot, Acorn came to Mickaboo in May 2023 in a box labeled “angry conure.” San Francisco Animal Care and Control had discovered him battered and unstable, with his head tilted more than 90° sideways—a clinical sign of bromethalin poisoning. Torgerson volunteered to transport Acorn to an avian vet, but despite care, Acorn died one month later.
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That wasn’t the end of Acorn’s story. Torgerson and Robinson, an evolutionary geneticist (she has since moved on from UCSF to Princeton), had previously approached Mickaboo’s then CEO, Sarah Lemarié, to collaborate on a study to satisfy personal and professional curiosity: What exactly are these birds?
“I thought: Wow, here we have a small number of individuals that have founded a population outside of their native range,” explains Torgerson. “OK, how did they get here? Where are they from? What’s their nature? Are they actually wild birds?”
To answer these questions, they needed a key—and missing—component: a complete, high-quality reference genome for a flock member. Acorn’s tiny body provided the research team with the first complete genome sequence of a San Francisco red-masked parakeet.
A bird’s genome is about one-third the size of a human’s, but sequencing it for the first time is still like putting together a “million-piece puzzle,” says Robinson. “Imagine you wanted to read a book, and a friend gave you a book that had gone through a shredder, and you needed to recreate the book by finding overlapping shreds that you can piece together into sentences, then chapters,” she says. “That’s what we’re doing when we create a genome for an organism for the very first time.”
It starts with a biological sample. (You don’t need a whole bird—a feather will do—but more genetic material is helpful.) Lab technicians prod it with pipettes and bathe it in solutions to extract its DNA, which is fed to a machine that produces strings of letters: A, T, C, G, representing adenine, thymine, cytosine, and guanine. These are the bases of a DNA strand, which instructs amino acids to fold into proteins, then cells, then organs, bones, beaks and feathers. And eventually, you have a bird.
After sequencing Acorn’s genome, the team gathered samples from 21 San Francisco parrots in vet and foster care—like Julian and Mooshi, two wobbly, charming bromethalin-poisoning survivors in long-term care with Torgerson. They also retrieved samples from two wild parrots belonging to a separate flock in Sunnyvale and Palo Alto, plus one pet red-masked parakeet.
Then, base by base, the researchers compared the samples to quantify the variability within and between individuals.
Not only did San Francisco’s free-flying parrots have distinct ancestry from the other birds, each sampled parrot carried DNA from red-masked and mitred parakeets. (An upcoming paper on the genomic research will include samples from an additional 20 birds). The mitred DNA ranged from 5 to 38 percent per individual. It’s an unlikely combo, because mitred parakeets typically inhabit the inland mountains of Peru, Bolivia, and Argentina—far from the coastal forests preferred by red-masked parakeets. Without human intervention, these species would probably never meet. And this hybrid genome was proof of the interspecies matchmaking that keen parrot observers had already observed. They could even identify the likely mitred matriarch: Olive.
Olive mixes it up
Olive “was born in South America, captured, and sold here as a pet,” says Mark Bittner, author of The Wild Parrots of Telegraph Hill, a 2004 memoir chronicling his years watching the flock. Bittner met this feisty mitred parakeet in 1995, when the flock numbered about 30 individuals of red-masked parakeets, fondly referred to as “cherry heads.” A band on Olive’s leg suggested she’d been legally imported. Bittner noticed she was different. She was larger than the rest of the flock, with a bigger beak, and her cry was distinct; it reminded Bittner of a seagull. And she was a pain in the cloaca, provoking fights over bowls of bird seed.
The spring after her arrival, Bittner saw Olive paired with a red-masked male he named Gibson. By the end of the summer, they’d produced Picasso, the flock’s first known hybrid baby. (The feathered family features in The Wild Parrots of Telegraph Hill, a 2003 documentary directed by Bittner’s future wife, Judy Irving; Bittner died in March.) Bittner recalled Olive reproduced every year. Soon, her babies had babies. Mitred genes flowed through the San Francisco flock.
Olive was not the first outsider to fly with the flock; blue-crowned parakeets had been seen in their midst. Today, many misplaced avians fly Bay Area skies, including the unrelated parrot flock in Sunnyvale. Yet Olive’s genetic integration appears exceptional. “The genome tells us there’s probably not migration into the flock,” Torgerson says. In fact, of the 21 sampled birds, the genomes show that each member of the flock is, genetically speaking, “kind of like cousins,” she adds.
“Basically, every member of the flock is somehow related to [Olive],” Robinson says. Although the genome cannot prove that Olive is the only mitred parakeet to contribute her genetics to today’s flock, it’s consistent with that theory. In other words, today’s flock is a large, extended family, rarely mingling—at least reproductively—with other escaped or wild-born Bay Area parrots. Despite their resemblance to their caged cousins, the genomic data confirms that San Francisco’s parrots are a distinct breeding population.
Every species has its own evolutionary origin story. The story for red-masked and mitred parakeets includes, at some unknown point in the distant past (a “few million years ago,” Robinson estimates) a common evolutionary ancestor. Gradually, that original Psittacara flock drifted apart, allowing today’s red-masked and mitred parakeets to develop unique characteristics in their homes in Ecuador, Peru, Argentina, and Bolivia.
By that logic, Olive’s contributions to the San Francisco flock could be something of a genetic family reunion, Torgerson muses. Her babies may not be creating a never-before-seen hybrid as much as they are recreating a modern interpretation of that ancestral species, at least in part, on a new continent.
Species, schmecies?
While this particular genetic mixture is unusual in both San Francisco and South America, “hybridization happens in wild animals a lot—especially in birds,” says Whitney Grover, director of conservation for the Golden Gate Bird Alliance. When distinct species share overlapping ranges and enough of the same mating preferences, hybridization may even confer advantages. Western gulls (Larus occidentalis), for example, share breeding ranges with glaucous-winged gulls (Larus glaucescens) along the West Coast, and their hybrid offspring seem to enjoy greater reproductive success than either of the parent species.
The hybrid offspring of Olive and her red-masked suitors, for their part, always seemed friendlier than their parents, at least according to Bittner’s observations: he lacks scientific backup, he concedes, “but the hybrid babies were always more trusting.”
The rest of the San Francisco flock’s behavior is as unique as their genome. “I think there is a deeper culture for the ones in the wild than the ones I’ve seen that imprinted as pets,” Torgerson says. “I don’t think that has to do with genetics; I think that has everything to do with experiences. They know each other. They remember prior activities. They hold grudges; they also hold each other dear.”
They even have their own language, so to speak. In past years, Lemarié says, if she was unsure about a Mickaboo intake’s lineage, she’d bring them home and watch them talk. They’d either warm up to her parrot from the pet trade, or chatter with the wild parrots convalescing at her house. “They speak a different dialect,” she says. “Once they start responding to a bird in the house, you can tell if they’re vocalizing like a wild parrot or whether they’re talking to the pet one.”
Today, the flock numbers between 250 and 300 individuals, Torgerson estimates—that’s up to a tenfold increase from the small flock Bittner was tending when Olive arrived on the scene. The Wild Bird Conservation Act effectively banned the trade of most wild-caught birds in 1992, so it’s unlikely that any of the parrots flying San Francisco skies have ever seen the coasts of Peru and Ecuador, or the mountains of Bolivia or Argentina. Instead, they are committed urbanites whose numbers are slowly but surely growing in San Francisco’s not-exactly-tropical ecosystem. And as it turns out, the city offers plenty of their favorite real-estate amenities.
The parrots have transferred their preference for canopy dwellings from tropical trees to tall buildings—they’ve been known to lark around the pole atop the Scientology building in North Beach. What’s beneath them doesn’t seem to matter much: the vines and shrubs of dryland forests are replaced by the pavement, grass, and passers-by of the city. They still build their nests in holes within trees, but have swapped the robust trunks of ceiba for the ornamental imported palms that dot our cityscape.
While their ancestors probably couldn’t tell a pine cone from a traffic cone, Italian stone pine—another import—is a local delicacy: older individuals teach the young to liberate the nuts with their beaks. They know where to score diverse cuisine, from balcony feeders to pyracantha and cotoneaster berries, and they cycle their foraging with the seasons: “They’re aware of fruit trees and berry bushes and when those fruits are ripe and when those berries are coming in,” says Irving. It’s not uncommon for the flock to suddenly, noisily swoop into a neighborhood after months of absence depending on what’s growing in the garden.
So do all these differences—genomic, ecological, even cultural—make them a new species?
“Biologists love to argue about what is and isn’t a species,” says Robinson with a shrug. Torgerson also demurs: “Tell me what you define as a species,” she answers. To them, revising formal taxonomy isn’t the point of the research. It’s more interesting to see how, and if, the data reshapes our relationship to the flock.
How to help the parrots
After the parrots got famous, Bittner noticed some of them disappearing. He suspects that, as members of the flock became accustomed to taking food from humans, people were absconding with the most trusting birds. Lemarié has seen this dynamic unfold many times. “The combination of adaptable, intelligent birds, and humans’ urge to develop bonds, quickly becomes problematic,” she says. The wild flock enchants human observers, who offer food, which the parrots accept. Humans name them, and get protective. They begin to think “their” birds need them.
“We think of parrots as domesticated animals because we keep them as pets, but parrots are definitely not domesticated,” Grover says. “They have not gone through that long process of being selected, over thousands of years, for the characteristics that make them good at living with humans.” That fact is likely clear to anyone who has watched them squawk and squabble at top volume above city streets.
The genomic study confirms not only that these parrots are not only hybrids but that they are a “breeding, wild population,” says Torgerson. “They are taking care of themselves. We shouldn’t take them out of the wild. And they need to be respected.”
“We’ve taken so much of their world from them. And now they’re adapting, which is incredible, and resilient,” Grover says. “But we should also think about, in a hands-off way, how can we let them thrive in a more natural way?” Experts all said the survival of this hybrid flock in San Francisco depends on humans learning to translate their affection into more helpful actions. When members of the flock disappeared, advocates including Bittner and Irving successfully pushed for a law banning public feeding. When a private tree trimmer accidentally evicted fragile nestlings from a palm tree nursery, Mickaboo volunteers got the City to halt palm-trimming during nesting season.
“My hope would be that, like every immigrant to the city—-we all are immigrants to the city, including these birds—-that they would continue to thrive,” says Irving. “And that the human immigrants would take special care to make sure that these birds stay wild, and stay free. I think that is what we want for ourselves, too.”
