Thursday, November 22, 2007

Hummingbirds in the snow

Hummingbirds in the snow…I'll admit, that seems like an avian non sequitur, since everyone knows that hummingbirds are the jewels of summer, little tropical hothouse birds that would faint at the first hint of cold weather, never mind an actual flake or two of snow.

Which is why I especially love days like this past Sunday, when I was driving over the Kittatinny Ridge in heavy snow showers. Down in the valley an hour south of my house it was slightly warmer, and the snow was coming down as rain, while I set up a cage trap on the porch of a lovely old 1800s farmhouse. A nectar feeder hung inside, and within minutes, I'd trapped an immature female Selasphorus hummingbird, which Deb and Jim, the homeowners, had spotted a couple of days earlier.

If that seems remarkable, it isn't; western hummingbirds have become commonplace in eastern states like Pennsylvania every fall and winter, often lingering until well past Christmas, and through nights when the temperature may dip below zero.

In fact, the only remarkable thing about this situation was that this was the second hummingbird to show up at Deb and Jim's home this month. A week earlier, my colleague Wayne Laubscher of Lock Haven (covering for me while I was out of town) had banded an immature male rufous hummingbird here, a sparkling bird the color of a new penny, with its fiery orange gorget almost completely molted in. The little guy was still hanging around on Sunday when I was there, and buzzed us a couple of times after we had the trap set up.

A rufous hummingbird, banded in late December 2004, Middletown, PA (©Tom Johnson)

Once I had caught the new hummer, it was a matter of about five or 10 minutes to band her, take a few measurements, some photographs, and then release her. The measurements allowed me to make a firm identification; female and immature hummingbirds of the genus Selasphorus are almost impossible to identify in the field, but by measuring the width of her outermost tail feathers, her wing and bill, and by looking for a distinctive notching in one of the central tail feathers, I confirmed that she was a rufous hummer, and not one of the look-alike Allen's or broad-taileds.

Wait a minute, though – what would any of those decidedly western species be doing in Pennsylvania, especially on a snowy, late-November day? The answer appears to be bound up with the rapid development of a new migratory route, and a glimpse of avian evolution in action.

Traditionally, all of these species – rufous, Allen's, calliope, black-chinned, broad-tailed and others – nested in the U.S. and Canada but wintered primarily in Mexico. To get there, they follow a genetically coded orientation that propels them south in fall – flying individually, not in flocks or with their parents, depending solely on the instinct inscribed in their DNA.

But DNA mutates, and when it does, sometimes you get birds that head in the wrong direction. That's probably what's happening with these hummingbirds; programmed to head east instead of south, they wind up in the mid-Atlantic states in autumn, then work their way down to the Gulf Coast, where thousands and thousands of them now pass the winter.

By catching and banding these birds, which may be recaptured miles or years later, we can document this evolution of a new migratory route and wintering ground. I'm one of a loose network of hummingbird banders in North America studying this phenomenon, and at this time of year, I'll drop everything to race out and band a newly reported hummingbird.

On Wednesday I drove to northern New Jersey to band what is only the fifth calliope hummingbird to be seen in the Garden State. This little immature female (calliopes, which weigh about 3 grams, are the smallest birds in North America) was snugged down in a small but lavishly landscaped backyard in Denville, where dozens of birders had been coming to see her.

She was a snap to capture, and calm in the hand as she got her own, custom-made band, a minute thing only 5.4mm long, hand-crafted into a neat circle and laser-printed with a serial number, N99797. The bands are so small it takes more than 5,500 of them to weigh an ounce, and are no hardship for the bird.

Within a few minutes of her release, she was feeding again at one of the feeders, her movements followed by several big telephoto lenses. At night, like all of these cold-hardy westerners, she'd be tucked in a dense thicket, where she'd turn down her internal thermostat from a daytime high of about 109F to about 50F, going into a profound, death-like torpor to save energy. (That's why these western hummingbird species, which can be found above 9,000 feet in the Rockies and as far north as the Kenai Peninsula in Alaska, are not bothered by sub-freezing temperatures in the East. If they're healthy, they can even tolerate lows below zero for a few nights.)

A couple of times she zipped out from her perch to snag a small, passing insect – even in cold weather, these birds are adept at finding invertebrates, often picking dormant bugs out of foliage and from the crevices in bark. Nectar, either natural or from a feeder, makes up less than half of their diet at all times of the year.

The calliope was in good shape, except for some missing throat and tail feathers, perhaps from a collision with a wire or twig, which she would soon replace. And I was just in time – she apparently left this morning, Thanksgiving, a lovely, mild day and a perfect one for heading south. She took with her a tiny band – and my thanks, naturally.


BT3 said...

Scott: Great post and fabbo blog! Glad you're joining the blogosphere. The world needs to hear from you on a regular basis!

As the esteemed governorof "Cullyfornia" once said: "I'll be baaak!"

Rufous27 said...

I wouldn't have believed it if I hadn't seen it but it's really true that Rufous hummingbirds can handle the cold. Here's video of my feeder last night in 18 degree temp, with snow on the ground.

javieth said...

I must to say i love the snow, the cold climate, although i´m not a child anymore i remember my happy childhood and all the beutiful time that i spent with all my friends. Now when is snowing i prefer to spend my time with my boyfriend, most of all that he decided to buy viagra, we enjoy all the time.