Winter Hummers

It was New Year’s Eve morning and a cold one—barely out of the single digits—and old, crusted snow crunched rock-hard beneath my boots. The wind was keening from the North, and occasional snow squalls blotted the sun, obscuring the low central-Pennsylvania mountains. I tried as best I could to stay in the protected lee of this small, tidy home, while keeping an eye on the backyard feeder where a rare bird had been reported.

I’ve shivered and frozen many times while chasing a bird, toes numb and nose nipped by cold. Lots of us have—but usually not, as was the case on this cold December 31, for a hummingbird.

Wait a minute. A hummingbird? In the North, in the snow, in the middle of winter?

Yep.

A few moments later, a small blur whizzed into view—green and white, with a splash of rusty orange on its tail. It took a drink from a plastic feeder positioned under a heat lamp, then rocketed to an old apple tree where it sat and watched the yard with a jealous eye. When a chickadee flew to the nearby seed feeder, the hummingbird launched a frontal assault amid a barrage of angry chips, driving off the larger bird before returning to its perch.

I’d seen enough; it was time to get to work. I wasn’t there to watch, but to learn more about why such a seemingly unlikely scene is actually increasingly commonplace.

In my most recent column I wrote about my work with northern saw-whet owls, which has occupied my autumn nights for more than two decades. This time, I want to share what keeps me hopping during the day at that same time of year—chasing vagrant hummingbirds that are badly out of range and (at least to the casual eye) badly out of season. It’s a fascinating story, because in addition to being shockingly hardy, these little hummers have a lot to teach us about the dynamics and evolution of bird migration.

More Than Rubythroats

Birders have long taken it for granted that there is just one species of hummingbird in the East: the ruby-throated. That’s certainly true during the summer, when the farthest east any of the other 15 or so species of hummers extends is the middle of Texas, where black-chinned hummingbirds breed, as do buff-bellieds in South Texas. Otherwise it’s rubythroat country all the way from the eastern Great Plains to Florida and Nova Scotia, with a small but expanding beachhead in southern Newfoundland. (And this “eastern” bird also extends well west in the aspen forests of Canada, all the way to southern Alberta and occasionally British Columbia.)

But fall and winter are a different story. More than a century ago, ornithologists began noting a few otherwise western hummingbirds showing up far out of range. Initially dismissed as lost oddities, those pioneering birds have grown with the years into a seasonal horde, especially in the Southeast, where more than a dozen species have been found, and one, the rufous hummingbird, is now a fairly common backyard fixture in fall and winter. Farther north, all the way up to the Great Lakes and New England, rufous hummers and some of their regional relatives have also become increasingly routine, even in weather that makes a well-bundled human think twice about going outside.

Back at my car, I grabbed a wire-mesh cage trap the size of a large wastebasket, my banding box, and a tote bag full of gear. In a few minutes I’d placed the trap, feeder hanging inside, where the hummer was accustomed to feeding. As I was organizing my equipment, the hummingbird zipped in to investigate. After making a few cautious circuits around the trap, it flew in and landed. After allowing it a nice, long drink, I triggered a remote in my pocket, and a radio-controlled tripper dropped the door to the trap.

Reaching inside, I found a lovely adult female rufous hummingbird, her head and back iridescent green, her outer tail feathers bright chestnut. In the next five or six minutes I gave her a tiny leg band with a unique serial number, took some quick measurements, noting that she had heavy fat deposits and weighed a pleasingly plump 4.12 grams (0.14 ounces). After a few photos I carefully slid her onto the outstretched palm of the elderly gent whose home she was visiting. She lay there for a second or two, then exploded into flight, looping back to her favorite perch in the old apple tree.

What’s Going On?

So what’s going on here? A field guide shows that rufous hummingbirds usually range from western Montana to Oregon and southern Alaska, and then migrate south in a broad swath from the Pacific to Texas to their traditional wintering grounds in the mountains of western and central Mexico. But through the first half of the 20th century, records of rufous hummers steadily accumulated throughout the East, especially in Florida. (Actually, because many of these are sight records and it’s almost impossible in the field to distinguish female and juvenile rufous from the closely related Allen’s hummingbird of the Pacific coast, it’s probably best to classify many of these sightings as Selasphorus hummers, the genus to which both species belong.)

The slowly rising tide of westerners caught the attention of the birding community, but the hummers were generally written off as lost misfits, doomed to a bleak end. Most birders and serious ornithologists considered them a curiosity and nothing more. When a former zoology student named Nancy Newfield decided in 1979 to study them in Louisiana, she was privately—and at times publicly—ridiculed for wasting her time, although the late Bob Newman, the curator of birds at Louisiana State University’s natural history museum, encouraged her study.

Teaching herself how to catch, handle, and band hummingbirds, Newfield began to document a remarkable story of survival and range expansion, a project that continues today, almost 40 years later. Far from dying off, these hummers were coming back year after year, refuting the assumption that they were dead-enders. The number and diversity of hummers returning to the same yards in the Southeast where Newfield (and later, other banders she trained) worked rose year after year and decade after decade. Much of that later work was spearheaded by my good friends Martha and the late Bob Sargent in Alabama, trained by Newfield. They founded the Hummer/Bird Study Group and in turn trained dozens of banders from Texas to the Northeast.

The numbers are pretty amazing. My colleagues Fred Bassett, Doreen Cubie, and Fred Dietrich, who work together as the nonprofit Hummingbird Research Inc., have banded more than 3,000 individuals of 11 hummingbird species in Alabama and Florida alone, including rufous, Allen’s, black-chinned, ruby-throated, buff-bellied, Calliope, Anna’s, white-eared, broad-tailed and broad-billed hummers. (Three more species—magnificent, Mexican violet-ear, and green-breasted mango—have been banded elsewhere in the Southeast, and my colleague Sandy Lockerman banded a Bahama woodstar, of all things, in Pennsylvania.)

But by far the most likely western vagrant to show up in the East and Southeast is the rufous hummingbird, thousands of which have been banded—and many, many more observed—over the past couple of decades. And as with much of migration, the reason they’re in the East probably all comes down to instinct and genetics. Birds don’t need to learn to migrate, and except for a few groups like waterfowl and cranes, where young birds travel in mixed-aged flocks and can learn specific routes and stopovers, most birds hatch with a preset, genetically coded set of instructions that compels them to fly a specific direction at specific times of year. Thus, a young rufous hummingbird coming out of the egg along Prince William Sound in Alaska already has a migratory template stamped on its genes that will aim it toward, say, Michoacán, Mexico, come autumn.

Unless, that is, something goes wrong. Anything genetic is subject to mutation, and a tiny, tiny fraction of the rufous hummingbirds born each year will have a hiccup in their software, one that sends them in the wrong direction—east, for instance. In all likelihood, this has been going on for as long as rufous hummers have been migrating—and the harsh Eastern winters of previous centuries, combined with the inhospitable forested habitat, probably eliminated most of them. But today, with the climate warming, the landscape changed, and the Southeast in particular a garden-rich land of milk and honey for a hummer even in winter, those “bad” genes aren’t culled from the population. Instead, these misprogrammed hummers migrate back home in spring and spread those once-faulty but now beneficial genes further and further through the gene pool.

I completed my hummingbird training in 2001, becoming one of then only about 200 licensed hummingbird banders in North America, working together as part of a collaborative, continental effort to understand what’s happening with these birds. Each autumn we wait for the first reports to come filtering in—some from birders, but most from puzzled or frantic homeowners referred to us by wild bird stores, local Audubon chapters, museums, or nature centers, or who in desperation just Googled “hummingbird in winter” and came across our names and contact information. Many of the conversations begin with, “You’re not going to believe this,” but, of course, we do.

Here in the mid-Atlantic region, the majority of our reports come in October and November—observations usually peak a month or so earlier to the north, a month or so later in the Carolinas. By January, the bulk of the action has shifted south to the Gulf region, where it appears the majority of these birds spend the winter, having been pushed reluctantly south by the advancing cold. (More in a moment about how they can tolerate such conditions.) In a typical year, we may receive anywhere from a couple dozen to more than 100 reports of western hummers in Pennsylvania alone.

Hummingbird Bands

Banding hummingbirds, despite their size, is actually a pretty straightforward task; the methods and tools are much the same as for banding any bird, just obviously scaled down. I set my trap and wait—sometimes for seconds (I’ve had hummers fly into the trap while I was still positioning it) and sometimes for hours, or days. Some hummingbirds, regardless of age or gender, simply refuse to have anything to do with the trap.

The bands are tiny and handmade—the only bird bands that don’t come preformed by the U.S. Bird Banding Laboratory. Instead, I receive a 4-by-6-inch sheet of thin aluminum alloy, on which are laser-printed 100 alphanumeric codes (something like J05436) in 10 rows of 10 each. Using a heavy bench shear capable of slicing metal with precision, I carefully cut the sheet into strips exactly 1.48 millimeters (five one-hundredths of an inch) wide, each carrying 10 band codes. Then, with a specialized metal snip, I trim each strip into 5.6 mm lengths containing the codes, and finally form each of these into neat, round bands using a custom-made jig. Each band gets a final quality check under high magnification to make sure there’s no rough burring or sharp edges; to make a full string of 100 takes me about two hours. Once in place, the band weighs about as much, proportionately, as a man’s wristwatch weighs on an average guy.

Surviving Winter

Most of the hummers we band leave the Northeast once seriously cold weather arrives in late November or December, but some actually overwinter as far north as New England. Their resiliency in the face of the cold is nothing short of astounding. Frigid temps are a danger for any small bird (including northern insectivores like kinglets and creepers), but there’s a particular risk for such a minute creature as a hummingbird, especially given its extraordinarily high metabolism. Maintaining that internal furnace during the day requires constant feeding; on a cold night, trying to do so would deplete all a hummer’s energy reserves, and it would be dead of starvation by morning.

But many hummers have a nifty metabolic trick—the ability to slip into deep torpor at sunset, lowering their body temperature from about 100.4 Fahrenheit to about 50–55 Fahrenheit, becoming rigid and unresponsive. Having turned down the thermostat, the bird needs far less energy to survive the night, and at daybreak, it rouses, restokes its internal fires, and roars off to feed. Consequently, species like rufous, Allen’s, Calliope, Anna’s, and other western hummers can tolerate nighttime temperatures at or below 0—sometimes dramatically below. My colleague Wayne Laubscher banded a female rufous hummingbird in central Pennsylvania a few years ago that survived nighttime lows of minus 9 Fahrenheit, with windchills of minus 36 Fahrenheit, during an exceptionally harsh cold snap. (Rubythroats appear to lack the ability to go into deep torpor, but as more and more winter along the Southeastern coast, banders are finding a surprising tolerance for cold among that species, as well.)

During the day, winter hummers frequently use artificial feeders, which hosts often rig with heat lamps to keep the sugar water thawed. But despite concerns that such feeders “trap” hummingbirds in the North, or that the birds should be “rescued,” there’s no evidence that they require intervention. Even in winter there is plenty of natural food for these highly insectivorous birds, including cold-hardy arthropods such as midges and springtails, hibernating bugs and spiders to be pulled from bark crevices and the like, and the sap that leaks from sapsucker drillings.

Miraculous Migration

A hummer that has already migrated thousands of miles to get to an eastern yard is hardly likely to “forget” to keep migrating on. What’s more, a rufous hummer with a full fat load, like the one I caught that New Year’s Eve morning, is capable of flying roughly 600 miles nonstop in about 24 hours, just by relying on its on-board reserves. (Rubythroats can do the same thing, crossing the Gulf of Mexico.) When it’s ready, a hummingbird can swap the snow squalls of Pennsylvania for the balmier climes of, say, central Georgia, in about a day. But like many migratory populations, a few individuals are programmed to stay as far north as possible—which can be a risky strategy if the weather turns bitter.

In the main, though, this new migratory route and new eastern wintering area seems to be working pretty well for western species like rufous hummingbird. Like the Old World warbler known as the blackcap, which has been undergoing a similar expansion into a new winter range with a new migratory path thanks to similar genetic mutations, what’s happening with hummingbirds provides both an example of how dynamic bird populations can be and a window for scientists into how new migration patterns may evolve.

You can help with this understanding. If you feed hummingbirds in the East and Midwest, keep a feeder up and fresh through at least Thanksgiving (and hanging where you can easily see it, so you’ll know if you have a visitor). If you’re in the Northeast, Great Lakes, or mid-Atlantic regions, and you have a hummingbird of any sort after Oct. 15 (Nov. 15 in the South and Southeast), get in touch with one of the collaborating hummingbird banders listed on the Hummingbird Research website, hummingbirdresearch.net/p282.html.

The process is quick and doesn’t harm or chase away the hummingbird. Best of all, the data from your banded bird will help us better understand the ways hummingbirds are adapting to a changing world, and how their movements and migrations are rapidly shifting. And you’ll have a personal window onto one of the most exciting developments in ornithology in recent years.

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