One of the most famous passages ever penned by Aldo Leopold goes like this:
One swallow does not make a summer, but one skein of geese, cleaving the murk of a March thaw, is the spring.
He goes on:
A cardinal, whistling spring to a thaw but later finding himself mistaken can retrieve his error by resuming his winter silence. A chipmunk, emerging for a sunbath but finding a blizzard, has only to go back to bed. But a migrating goose, staking two hundred miles of black night on the chance of finding a hole in the lake, has no easy chance for retreat. His arrival carries the conviction of a prophet who has burned his bridges.
Fast forward to the 21st century. All over North America—increasingly, these days, all across the northern hemisphere—geese “migrate” from golf courses to corporate headquarter lawns.
But I get the point. I see what Leopold is getting at, even if the movements of geese today signify something very different. Leopold’s point is this: We birders—we naturalists—mark the passing of the seasons by certain avian auguries.
In my home state of Colorado, the Rufous Hummingbirds started showing up a couple of weeks ago. These feisty hummers do not breed in Colorado. Neither do they migrate through in the spring. They’re fall migrants, plain and simple. Even though their “fall” migration begins just a few days after the summer solstice, they are unambiguous harbingers of autumn. They are—in their own way—every bit as exemplary as Leopold’s skein of geese. (Right: Photo by © Bill Schmoker.)
Rufous Hummingbirds are not, however, the first to get back. Here in Colorado, fall-migrant Marbled Godwits arrive even earlier than the first Rufous Hummingbirds. In most years in Colorado, the first Marbled Godwits are noted pretty much right at the solstice. But there’s a hitch. Godwits, you see, are fairly common spring migrants through Colorado. They’re still passing through in late May. When the godwits “return” in late June, they’ve been gone for just a few weeks. It’s different with the Rufous Hummingbirds, reappearing for the first time in more than eight months. Marbled Godwits are subtler auguries, I think it’s fair to say, than Rufous Hummingbirds. (Left: Photo by © Bill Schmoker.)
And Bullock’s Orioles are subtler still. Here’s the deal. They haven’t gone anywhere at all. Unlike Marbled Godwits, which are gone for at least a few weeks, Bullock’s Orioles are present in Colorado all summer. But if you’re attentive to the avian annual cycle, you come to appreciate the Bullock’s Oriole for being a sure sign of autumn. Around the middle of June, adult male Bullock’s Orioles start to move off the breeding grounds in Colorado; these birds are “molt migrants,” beginning their annual “molt migration” to molting grounds in the Desert Southwest. Toward the end of the second week of June, you start to see them in the “wrong” places—on yucca flowers out on the plains, instead of in leafy treetops along streams and rivers. As an emblem for the new season, the Bullock’s Oriole is, I submit, a bit like Leopold’s cardinal or chipmunk. (Above: Photo by © Bill Schmoker.)
Which brings me to an even subtler—far subtler, I would say—first sign of fall. I noted it at 6:42 a.m. yesterday morning, Sunday, July 17th. I was birding, barely birding, along a busy road in surprisingly bustling Louisville, Colorado. Then I heard it: high-pitched, a tenth of a second, and then it was over. It was the flight call of a Chipping Sparrow. Chipping Sparrows do not breed in Louisville. They breed within ten miles of Louisville, in the steep foothills of the Front Range, just to the west. But not right in Louisville. A few will stop over in Louisville, but most will proceed eastward quite a ways—to eastern Colorado and western Kansas, where they complete their annual molts. Like Bullock’s Orioles, Colorado’s Chipping Sparrows are molt-migrants—a fact that was discovered just a few years ago.
(Right-click here to listen to the flight call of the Chipping Sparrow. Audio recording by © Michael O’Brien.)
A Bullock’s Oriole, jet black and blaze orange on a yucca, is hard to miss. Same thing with Leopold’s cardinal. But the flight call of an unseen Chipping Sparrow—now that’s obscure. Even if you know the brief, high-pitched call, it’s easily missed, lost amid all the other sounds of a summer morning. It’s over in the blink of an eye…and that's an odd way of putting it, as there’s nothing to see.
The flight call of the Chipping Sparrow is arcane knowledge. But isn’t that a large part of the allure of birding? It’s marvelous, it’s wonderful—isn’t it?—to begin to realize that there’s much more out there than we ever knew. It’s what sustains us, after all these years, as birders. But it’s also what got us started in the first place.