The sound echoes from the marshes behind my house every morning, starting in late February: konk-a-REEE. It’s an alarm clock of sorts — it signals the start of a new day and a new season.
This is the song of the red-winged blackbird, an abundant summer marsh bird that leaves the Outer Cape in midwinter. They return in big numbers in February and stay well into the late fall. And as beautiful as they look with their silky black plumage and red epaulets, nothing compares to hearing their song on a cold spring morning. It is the essence of spring distilled into a two-second sound.
I love birdsong. I miss it in the fall and long for it in the winter. Now, as birdsong begins to bloom across the Outer Cape, I can immerse myself in it. Don’t get me wrong, I love looking at birds, too, but hearing them sing feels so personal, particularly as I’ve grown more familiar with these vocalizations. It’s a nostalgic feeling, hearing an eastern phoebe or a common yellowthroat singing; the songs take me back to a birdy spring morning the same way Mumford & Sons takes me back to middle school.
We take for granted that birds sing. But what other animals around here do? Yes, frogs, toads, and some insects like cicadas make noises, but the complexity of birdsong is special.
Step out into a wooded area on the Outer Cape and you’ll hear an exceptional variety, including the rolling TEA-kettle TEA-kettle TEA-kettle of a Carolina wren echoing from the underbrush, the whistled peter-peter-peter of a tufted titmouse in the treetops, and the nasal eeen-eeen-eeen of a red-breasted nuthatch. That diversity is remarkable — something you don’t get elsewhere in the animal kingdom.
Birds produce sounds using their syrinx, a specialized organ located where the trachea branches in two bronchi to meet the lungs. By vibrating the walls of this part of the trachea, birds can produce incredibly varied sounds, from the rambling chirps of the ruby-crowned kinglet to the high-pitched whistle of a Cape May warbler.
The syrinx is an especially versatile organ because it can constrict and bend the airflow from the left and right branches of the lungs separately. This allows most birds to produce two different sounds simultaneously by using air from the left lung to produce one sound and air from the right lung to produce another. That’s how cardinal songs, for instance, can sound so rich and switch between pitches so quickly.
Birds evolved songs mostly to attract mates and to establish territory, though they might also sing to strengthen their pair bonds or to squabble with invaders. Songs differ from calls mostly through their complexity — songs are typically longer and more detailed, while calls are shorter and punchier.
While all birds call, only some birds sing. The main singers are the passerines, or perching birds, a group that includes chickadees, warblers, finches, sparrows, and around half of the bird species on Earth. Outside of the passerines, a handful of other species like cuckoos, owls, and whip-poor-wills also have vocalizations that function like songs.
The songs that birds sing are stereotyped, or fairly consistent, within a species, but some species have surprisingly extensive repertoires. According to the Birds of the World database run by the Cornell Lab of Ornithology, the dark-eyed juncos, gray and white sparrows that visit here in the winter and shoulder seasons, have seven song types, from a trill to a whistle series to a rambling warble that sounds like a goldfinch. Meanwhile, yellow warblers, summer visitors here, have as many as 17 songs.
A recent review led by Elly Knight of the University of Alberta found that most groups of birds also have individually identifiable songs. Humans can recognize some of these unique sounds. I know of the case of one Swainson’s warbler, a skulky brown bird from the southeast, that turned up in a park in New Jersey every year. Birders realized it was the same bird because its song had a distinctive three-pronged waver.
Like our speech, songs are typically taught to birds by their parents or other adult birds around them. And because songs are learned rather than genetically encoded, they evolve quickly, sometimes so quickly that we can hear it happen.
In the 20th century, the widespread ground birds called white-throated sparrows mostly sang a song that’s described with the mnemonic Oh sweet Ca-na-da Ca-na-da Ca-na-da — two rising whistles and three triplets. Then, in the late 1990s, according to a study led by Ken Otter of the University of British Columbia, a few sparrows in western Canada started singing Oh sweet Ca-na Ca-na Ca-na, turning the triplets into duplets. This version turned out to be catchy — sparrows on the other side of the Rockies started singing it in the mid-2000s, and by 2020 it had spread across the entire continent. That is, in 20 years, a continent’s worth of a bird species changed the way it sang.
The authors suspect that the birds taught each other the song on their wintering grounds. White-throated sparrows from different populations winter together and they sing soft “whisper” versions of their songs in the winter. Whether this is how the new song spread is hard to know.
Perhaps the most remarkable thing about birds’ songs is how much we don’t know about them. Why do birds sing so much at dawn? Do birds that live in the understory, singing through dense brush, change the way they sing to better suit that habitat? Why do birds have more than one song?
What we know for certain is the joy they bring people. In addition to the evidence from millennia of poetry and music inspired by birdsong, a recent study by researchers at the Max Planck Institute for Human Development and published in Scientific Reports found that listening to birdsong — even recorded birdsong — for just six minutes can alleviate feelings of depression, paranoia, and anxiety.
There is something therapeutic about the sounds that birds make, even though they don’t make them for us. To me, there may be no stronger evidence that we are all meant to be birdwatchers.
