An Outfield of Flycatchers

November 4th, 2010 | Meera

On April 17, 1822, while traveling in the prairie lands of southeastern Arkansas, John James Audubon discovered a small, rather drab little bird about the size of a sparrow. It had a crown and back of dark olive, two white bands across its wings, a pale gray throat and upper breast, and light yellow underparts. Though in appearance it was very nearly identical to several other birds already known to science, Audubon knew he had never before heard this distinctive two-note call, a high and rasping buzz which the creature let out repeatedly in flight. He identified it as a new denizen of a large family of tree-dwelling passerines known for swooping from branch to branch, deftly capturing insects on the wing. It was this skill that gave them their name: Flycatchers.

When, six years later, Audubon formally described his new avian find in an early edition of Birds of America, he named it “Traill’s Flycatcher.” This was a nod to the Scottish physician and amateur naturalist Thomas Stewart Traill, someone who had helped Audubon exhibit his drawings to an audience across the water in the years before the budding artist had become quite as famous as he was going to be.

The name was a thoughtful gesture—but one that did not last very long. In the years since Audubon made his discovery, ornithologists have separated Traill’s Flycatcher into two distinct species: Alder and Willow Flycatchers. The two are virtual twins, but have different voices. (That is, according to the books. I can tell I still need more practice as a birder, because they actually sound very similar to me—although the Alder has a call that more resembles a zipper being swiftly tugged, and the Willow one that is more like a sharp sneeze.)

Neither, in any case, has hung on to a common name that recalls Traill. Researchers agree that the bird Audubon saw that day was what we would now call a Willow Flycatcher. Only its scientific name, Empidonax trailli, retains a Latinized trace of the good-hearted man Audubon meant to honor. (Such is the caprice of species; for more on the scientific and philosophical underpinnings of classification, I urge you to read this post by the talented DeLene Beeland.)

Despite what some consider its unremarkable appearance, the Willow Flycatcher does have several notable qualities. A few, for instance, are capable of defending themselves against the brood parasitism of the Brown-headed Cowbird—which shares the cuckoo’s disagreeable habit of laying its own eggs in other birds’ nests and abandoning them to the care of unsuspecting adoptive parents. According to a number of observers, Willow Flycatchers that find cowbird eggs in their nests have been known to bury the unwanted artifacts. They do this by pushing the alien eggs into the bottoms of their nests and adding more material on top—effectively entombing them within a new layer of nest lining. It’s not clear whether the flycatchers do this strategically with cowbird eggs, or as a simple response to any foreign material within their homes; either way, it’s a pretty delightful response to a base attempt at moochery.

And unlike songbirds, parrots, and hummingbirds, each of which must learn their vocalizations from adult teachers, flycatchers—Willows included—emerge from the egg knowing the song dialects particular to their species. Even when young flycatchers are deliberately tutored with the songs of similar but unrelated species, what comes out of their beaks when they begin to call is emphatically the sound of their own kind. Confuse me not with your zipping pip, you Alder, for I am a sneezing Willow! They are examples, in other words, of birds whose mother tongues are somehow encoded in their genes. (I cannot tell you how much I envy them. I myself, lover of all discourse and code, know only about three words of Punjabi and about a dozen of Cantonese, the languages my parents’ families speak.)

I tell you all this, of course, because I prepared a Willow Flycatcher today in the bird lab, and was enchanted by the soft lemon-sorbet plumage it carries on its belly and the inside of its tail.

Willow Flycatcher

P.S. As Diana reminds us, Willow Flycatchers are fairly common birds. But the Southwestern Willow Flycatcher—one of the ten or so subspecies that populate the United States—has been on the decline for many years now, mostly as a result of habitat loss and fragmentation. It’s been classified as endangered since 1995. The story of its struggle to survive has taken some fascinating turns lately.

3 Responses to “An Outfield of Flycatchers”

  1. I assume Brown-headed Cowbirds leave their eggs in a variety of nests, and not just those of the Willow Flycatcher. Otherwise, there would be no cowbirds to speak of. Do you think the cowbirds will eventually figure out that their eggs are being buried (entombed) by the flycatchers, and that the projected returns make this an unhealthy investment?

    Thank you, as always, for delivering another fascinating piece of the world. You do all of the work, and we readers get to enjoy and learn, without effort — our own form of base moochery!

    • Meera says:

      Yes, cowbirds spread their interloping eggs far and wide!

      I like thinking of you as a base moocher, but to be fair I mooch off you, too. :)