How do they survive the cold?
“We think they’re basically pre-adapted to survive in cold climates because they build their own nests and they can vary their diets so dramatically across the year,” says Stephen Pruett-Jones, an ecologist at the University of Chicago, who has been studying birds for decades. “They roost in their nest every single night of the year, so the nest is really more like a home to the monk parakeet. And their diet changes completely during the winter to seed in backyard bird feeders.”
JILL LANGLOIS, “Former pet parrots breeding and thriving in 23 U.S. states” at National Geographic
Okay, not completely wild. But they have prior adaptations to serious sub-zero temperatures.
Paper. (paywall)
“The primates of the bird world… ”