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THE LONG REACH OF TINY BIRDS - Hummingbirds are inspiring new cross- border conservation efforts between Mexico and the United States - aiding hummingbird migration
National Wildlife, Oct-Nov, 2002 by Tim Vanderpool
SUNLIGHT escapes the thicket, pausing on a furious flash of red and green that careens through the damp morning air. "Oh, there's that rufous again," Marion Paton whispers to visitors, with a conspiratorial grin.
The rufous hummingbird ignores the nosy humans charting its dips and dives from a hushed corner of Paton's overgrown backyard. Instead, the bird's fierce black eyes focus on a feeder, one in a row of nine, all glistening like the dessert tray in a busy roadside diner.
"He's a hungry one, for sure," says Paton, a retired school-cafeteria manager who runs her Hummingbird Haven on two-and-a-half acres ringed by thick forest. A true hummer's Xanadu, the feeding station is situated in the tiny town of Patagonia, Arizona, amid verdant mountains some 20 miles north of Mexico.
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When migration is heaviest in spring and fall, this region becomes one of the most species-rich hummingbird hubs in North America. As many as 15 different kinds of hummingbirds visit Paton's lush oasis, from the irascible rufous to the broad-billed, racing by in a flurry of shimmering blues and greens. A few of these birds stick around during much of the year. But most others are just passing through for breeding season or a quick meal. "These birds really get to be family," Paton says, "and I love seeing them show up year after year."
But each year that journey becomes more treacherous for tens of thousands of these minute fliers, as crucial migration corridors are squeezed by urban development or degraded by heavy cattle grazing, which drives out many native plants on which the hummingbirds rely. Despite these threats, Paton says she hasn't seen hummingbird numbers dropping at her backyard rest stop--at least not yet. To ensure that never happens, a growing network of researchers and activists are now reaching across borders, cooperating on everything from habitat preservation and ecotourism to public education in Mexico.
Part of the problem of protecting hummingbirds is biological. Driven by notoriously raging metabolisms, these creatures rely on abundant flowering plants--spiced by insect appetizers--for constant meals. When flowers get scarce, fearsome territorial instincts take charge, says Bill Calder, a University of Arizona hummingbird expert and member of a research project sponsored by the Arizona-Sonora Desert Museum in Tucson. "We had a situation where one male rufous was guarding the only chuparosa plant, the only patch with any flowers," says Calder. "He was fiercely defending it. When the other hummingbirds were gone, he'd plop down on the ground exhausted."
You can see why backyard feeders might be a hungry hummer's Nirvana. "I go through six quarts of sugar water a day," says Paton. "They stop here to fatten up on their way south. Then we see them come back in March. It's like running a boarding house."
Author David Lazaroff puts this phenomenon in perspective. "Being a hummingbird is like driving a car with a one-gallon gas tank: There is an almost constant need to refuel," he writes in The Secret Lives of Hummingbirds.
The availability of food--whether from feeders, or the flowering chuparosa, morning glory and ocotillo--helps determine which migratory routes the birds choose. It also rules their short, furious lives.
You'd have a hearty appetite too, if you shared a hummingbird's vital stats. For example, it boasts the most rapid heartbeat for a bird-- nearly 500 beats per minute while resting, and 1,260 beats when in action. It weighs the equivalent of only a few dimes at most, but flight muscles account for nearly 30 percent of its total body weight. It also boasts the most rapid wing beats of any bird, as many as 80 beats per second, and goes into 60-mile-per-hour dives.
This high-octane lifestyle compels it to sip as much as one-and-a-half times its body weight in nectar daily. It also requires finely tuned travel skills; those hummingbirds passing through Paton's sanctuary must remember where to find the next lunch stop.
"It's really tantalizing to wonder how this little brain that weighs 200-odd milligrams can program all this stuff in there," Calder says. For hummingbirds, long-distance travel also requires pinpoint logistics. "If they put on maximum fat, they can cover 500 or more miles at a stretch," he says. "But according to all the notes I've collected, you don't see the high end of their weight range on northbound migration. This makes sense--if they put on a lot of fat, enough to go too far, they might overshoot the next filling station. It's sort of like when I'm going north over mountains, I don't try to have a full tank. Why, when I know there's a gas station on other side?
"The other problem is," Calder says, "if you have enough gas in your tank to go 200 miles north into winter where there are no flowers, then what do you do? If there's not a filling station there, you're screwed. Somehow, hummingbirds are factoring in these things."
Their timing must also be precise. "In a lot of situations, because of a long migration or because they're up high where spring doesn't come very early, they've got about a ten-week period in which to create nesting sites and breed," Calder says. So for some species, he adds, "there's not enough time to do it twice in one season."
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