From the first harsh (but oh-so-welcome) kong-ga-ree of a red-winged blackbird as early as late February, to the complex and voluptuous harmonic of a wood thrush in mid-May, our northern forest airwaves are dominated by birdsong in spring. The resurgence of vocal behavior by both returning migrants and hardy year-round residents revives our senses and stirs our souls.
No other animal group on the planet produces as many diverse and complex sounds – both vocal and non-vocal – as birds (although amphibians come close). Ornithologist Joel Welty, in his classic 1962 textbook The Life of Birds, put it exquisitely: “With an uncommonly lavish hand, natural selection has produced in birds an extraordinary variety of songs, calls, and other sounds.” Although a few species have no voice – storks, some pelicans, and vultures – the vast majority of birds emit vocal sounds of one sort or another. True songbirds, which comprise a suborder within the passerines, or perching birds, are far and away the most musically endowed avian group.
The stunning array of bird vocalizations is nowhere more apparent than in woodland habitats. Here, songs range from simple and short (the fee-bee of a black-capped chickadee) to elaborate and long (the cascading, vibrant refrain of a winter wren, which can contain 100 notes and last 10 seconds). Not only song structure, but vocal repertoires show head-spinning diversity. Individual red-eyed vireos, a ubiquitous northern hardwoods songster, may deliver more than 40 identifiable songs, although most sound the same to our human ears. Moreover, this species is indefatigable; a single male red-eyed vireo was recorded to deliver 22,197 distinct songs during the course of one day. Yet, this songbird’s vocal portfolio doesn’t hold a candle to the undisputed repertoire champion: one male brown thrasher is capable of singing more than 2,000 recognizable song types.
Spine-tingling splendor and endless variety aside, birdsong is spurred by urgency and necessity – and hormones. Birds sing to communicate, to transfer information. Songs, given primarily by males, are stimulated by hormonal changes brought on by increasing daylength and a single overarching goal: procreation. Specifically, songs serve to establish territorial sovereignty, entice mates with signals of vigor and dominance, synchronize sexual behavior, and reinforce the pair bond. Evolutionarily, avian song can act as a behavioral barrier that limits interbreeding of related species, thereby promoting speciation.
Not all birds sing with their voices. Some of the most extraordinary avian songs are produced mechanically. The rhythmic “drumming” of a male ruffed grouse results from wing beats of up to five beats per second as a bird displays his vigor atop a low log or stump. The adaptively stiffened outermost tail feathers of Wilson’s snipe create a tremulous, haunting whistle called “winnowing” when air pulsates through them during male aerial courtship flights. Woodpeckers “sing” by hammering their bills in species-specific cadences on resonant tree limbs or, to the occasional chagrin of humans, on metal roofs.
The dazzling “sky dance” of American woodcocks features both mechanical and vocal sounds, performed via a dizzying display flight to create a spectacle that everyone must experience at twilight on an early spring evening. First, the male utters a repeated, nasal, buzzy peent from a patch of bare (sometimes still snow-covered) ground. Then, without warning, he erupts in a spiraling upward flight, accompanied by musical twittering as air rushes through the outermost three narrow, stiffened wing feathers. At the flight’s apex 200 to 300 feet above ground, he stops and plummets, wildly zigzagging downward while emitting sounds best described as warbles and chirps (there is argument about whether these are vocal or wing-produced). Then, silence during the final 50 feet and a soft, often unseen landing at almost the exact spot of takeoff.
Whether woodcock, warbler, or wren, produced vocally or not, birdsong adds a layer of lushness to our northern landscape in spring. We mark time by the return of singing birds, delighting as the earliest announce themselves, exulting as the full symphony unfolds. Their chorus is truly among the greatest of nature’s many marvels.