UPPER WEST SIDE — The tiny hummingbird that's delighted nature lovers outside the American Museum of Natural History this winter is reportedly making the most of her time in the city.
While most of her fellow Rufous hummingbirds are sunning themselves in Mexico at this time of year, this one seems to have taken a liking to New York's colder climate. Locals have wondered how the miniature bird has survived weeks of wintry weather, but experts say it's not as unusual as it seems.
Despite their dainty appearance, hummingbirds are rugged, said Lanny Chambers, a St. Louis, Mo. field ornithologist who runs Hummingbirds.net.
"They're beautiful and iridescent and scatter the sunlight into a million colors, and they've been described as fragments of a rainbow, but they're quite pugnacious," said Chambers. "If they got to be the size of starlings, it wouldn't be safe to to go outside."
Hummingbirds are an "opportunistic" species which has been spotted stealing bugs out of a spider's web, eating the spider — then taking the empty web for their nest, Chambers said.
Among hummingbirds, it's the Rufous — the type spotted outside the museum — that's probably the most robust in North America. The Rufous' territory includes Alaska and the Rocky Mountains, and the cold doesn't bother them.
Chambers said he's found "fat, healthy" birds thriving after spending the night in sub-freezing temperatures in St. Louis.
Typically the Rufous breed in the northwest, then fly each fall across the Rockies to spend the winter in Mexico and, occasionally, in Gulf states like Louisiana. To prepare for the long journey, the birds, which usually weigh little more than a penny, pack on fat.
"It stops paying attention to sex and starts paying attention to food," Chambers said. Some birds have been known to double their body weight, he said. "They're little butter balls. They can barely fly."
But fly they do, across thousands of miles. Every year some birds, known as "vagrants," stray from the usual route. The number of vagrant Rufous hummingbirds in the New York area seems to be on the rise this year, said Phil Jeffrey, a birder who documents the off-course birds.
No one knows why, he said, though it could be linked to weather. "Rufous hummingbirds aren't supposed to fly across the Great Plains," Jeffrey said. "There's something really wacky about what drives these birds to go due east."
The Rufous hummingbird outside the American Museum of Natural History isn't the only bird that's gone astray this year in New York City. Several out-of-place species have been spotted, such as a Grace's Warbler in Long Island and a Yellow-breasted chat in Bryant Park.
"This winter has been very mild," said Paul Sweet, collections manager in the American Museum of Natural History's ornithology department. "(Birds) haven't been killed off, so birders have been seeing them. A lot of things that shouldn't be around are around."
The hummingbird at the museum is probably sticking around because she's found a steady food source in the bush outside the Rose Center for Earth and Space, Sweet said.
With wings that beat more than 50 times per second, the diminutive creatures require vast amounts of energy. If a human had a metabolism equivalent to a hummingbird's, they would have to eat 300 Big Macs a day to survive, Chambers said.
The birds can withstand cold temperatures by going into "torpor," a temporary hibernation where they slow down their heart rate and use less energy, Sweet said.
The one outside the museum appears to be a young female making her maiden migration, Chambers said. Hummingbirds make the trip solo, with no parents along to guide them.
It's possible she's acting on genetic instructions that told her to fly east and then stop in New York City, Chambers said. If that's the case, her odds of surviving aren't as good as a bird that flew to Mexico.
"The ones that have dysfunctional directions fall out of the gene pool real quick," Chambers said. "If it doesn't have an instinct to migrate, it's in trouble. And frankly, being cold-hearted about it, it's not supposed to survive."
Chambers called that scenario a classic case of natural selection.
But that hasn't stopped some bird lovers from trying to alter Mother Nature's plan. Shortly after the hummingbird was first spotted, wild bird rehabilitators showed up at the museum with nets, hoping to catch the bird and "rescue" it, said Sweet.
"They literally wanted to spend money to have it flown south or put in a greenhouse," Sweet said. "They feel like it's a hummingbird so it needs to be taken to the sunshine. I said, 'Look, it may die, but if it dies, that's nature. It's evolution. Those genes will not be perpetuated.'"
Sweet said the would-be saviors' time would be better spent trapping feral cats, which kill millions of wild birds each year.
Have you seen a hummingbird? Help scientists learn more about their migration patterns by submitting your sighting to a website that tracks the birds' annual travels using data from "citizen scientists."