As the days grow longer in spring, chickadees start singing a different tune. Besides the familiar chickadee-dee call, we now hear a whistled “hey, sweetie,” often answered by another chickadee: “Hey, sweetie! Hey, sweetie!” Soon a cardinal takes up the theme, “Come here, come here,” and later a bluebird, back from migration, joins in the chorus: “Ain’t I pretty!” By May, the orchestra, in full swing, fills the dawn with a symphony of birdsong. Why do birds sing so much in the spring? Why make noise that could betray your presence to predators? What role does birdsong play in the annual cycle of a bird’s life, to be worth so much energy and risk?
Many birds communicate with sounds. Ducks quack, geese honk, loons yodel, and songbirds sing. Some birds make non-vocal sounds, like woodpeckers drumming with their beaks or hummingbirds humming with their wings. Some birds are more musical than others. The songbirds are a group of passerine birds (small perching birds in the order Passeriformes) that are especially adept at singing. Songbirds include warblers, thrushes, sparrows, wrens, and finches, among others – over 4,600 species or nearly half of all birds worldwide. Among these are the virtuosos of the bird world.
Birds have a variety of vocal sounds for different situations. These are classified as either calls or songs. Calls are short, simple sounds that are innate, with important messages like, “Feed me!” “Predator alert!” or “I’m over here.” Calls are made by male and female, young and old, and they are heard all year long. Foraging in treetops, chickadees call out “tseet” periodically to stay in contact with flock members, while their “chickadee-dee” call alerts flock members of food or danger. Cardinals make a metallic “chip” call to warn of predators and warn off intruders. Some calls can be understood by other species of birds or even mammals. Mobbing cries of jays or crows let us know to look around for a hawk or owl. They are often joined by smaller songbirds, and together scold the predator loudly until it leaves.
How much information is communicated by simple calls? Quite a bit, as scientists are just beginning to discover. For example, chickadees give a high-pitched “zee” call when there is a moving predator, such as a hawk in flight, and a “chickadee-dee” call in response to a stationary predator. In addition, the number of “dees” at the end of the “chickadee-dee” call relates to the degree of danger – more “dees” for a small, nimble hawk, which poses a great threat to a chickadee, than for a large hawk, which is less agile and prefers bigger prey.
In addition to calls, many birds have a special song, a longer, more complex vocalization that is unique to its species. As the name implies, these are the more musical sounds made by birds, and they play an important role in the breeding cycle. They are sung in the spring by males on their territories. There are a few exceptions, like bluebirds, cardinals, orioles, and white-throated sparrows, in which the female has a spring song as well. After the young are fledged, birds usually do not sing again except occasionally in the fall when young males produce snippets of song, or “subsong,” as they learn the songs they’ll use the following spring.
Males sing both to defend a territory and to attract a mate. In the spring, males often return first from migration, and they jockey for position, each trying to defend a territory that will provide sufficient food and shelter for a family. To negotiate boundaries, they duel with their voices, holding singing contests with neighboring males. To a male, the song means, “Stay away, this is my territory,” but to a female arriving on the scene, the song means something like, “I’ve got some great real estate here. Come and be my mate.” Females are able to evaluate the fitness of a male and the richness of his territory – both critical for successful breeding – by his song. The song is a display, a signal that imparts important information to the listener. Singing lets males estimate an opponent’s strength and perhaps avoid an actual fight, and it gives females a way to choose among potential partners.
Unlike larger birds such as hawks, geese, and ducks, which mate for life, songbirds typically form a new pair bond each year. With short lives (six years on average) and high mortality during migration, they cannot depend on having the same partner each year, though it may happen accidentally because they return to the same nest site. Song serves to reinforce a pair’s bond with each other and helps them to coordinate the work of raising a family.
Songs are charmingly varied. The chipping sparrow’s song sounds mechanical, like a sewing machine, while the winter wren – whose song is the longest in our woods – sounds like tinkling bells. The robin’s lyrical “cheerio, cheery me,” contrasts with the ovenbird’s emphatic “teacher, teacher, TEACHER!” Songs can be nasal like the phoebe’s “fee-bee,” high-pitched like the white-throated sparrow’s “poor Sam Peabody, Peabody, Peabody” or full-bodied like the wood thrush’s melodic “oh lee, oh lay” phrases. The eerie, echoing triplets of the hermit thrush draw us into the woods like Pan’s flutes.
Though each species has a clearly recognizable song, many songbirds sing variations on the theme. Each songbird has a song repertoire which ranges from one to many songs. The chipping sparrow has only one song, while white-crowned sparrows have a few different versions. Marsh wrens have a hundred variations, and a brown thrasher may have over 2,000 different songs, the most variety found in any bird. Song variation allows birds to recognize each other individually. It may inform females about a male’s fitness in some way we don’t yet understand.
The vocal organ of birds is the syrinx, a bony structure in their windpipe with many fine membranes that vibrate when air passes over them. Birds with simple syrinxes, like pigeons or doves, can produce only simple cooing sounds. Songbirds, with more muscles and complex syrinxes, are the greatest musicians. Unlike our larynx, which is located at the top of the windpipe, a bird’s syrinx is located at the point where the windpipe forks into two branches (bronchioles). Birds can sing from one side or the other, switch from side to side, and some, like the thrushes, can produce two sounds at the same time.
Considering such a variety of sounds, we can’t help but wonder how birds know or learn to make them. All calls are thought to be innate, as are the songs of loons, ducks and geese, owls, pigeons, phoebes, and others. But in songbirds, they must be learned. Songbirds need to hear their own species’ song during a critical period in their development to be able to produce their song correctly when mature. They learn from the father singing near the nest or from neighboring males of the same species. By the first spring, most songbirds have perfected their songs. A few continue adding to their repertoire even after they are mature, like mockingbirds or catbirds, which mimic other birds or sounds in the environment.
In springtime, the dawn chorus is at its fullest. Like clockwork, each species begins to sing at a particular time, some before dawn and others later, reaching a crescendo by around 6:00 am. Many cease singing by mid-morning but then sing again in the evening, the sequence roughly in reverse. Sounds carry better without wind to distort them, and at dawn and dusk the air tends to be stiller and there is less ambient and human noise. It’s harder to forage in dim light, and perhaps the singing males are less exposed to danger and can risk advertising their presence. Though most singing takes place at dawn and dusk, some birds sing all day long. The red-eyed vireo’s quizzical “going up? coming down” is repeated over and over, one bird exceeding 22,000 times in a single day! Some birds, like mockingbirds or ovenbirds, will suddenly sing out in the dead of night for no apparent reason.
When days are long and food is plentiful, a bird’s fancy turns to courtship, if not love, and raising a family. Birdsong, so important to this part of their life cycle, is as complex and nuanced as a musical score. Listening to songbird songs is one of the joys of springtime and a good way of tuning in to the nature around us.
Elliot, Lang. The Songs of Wild Birds. Boston: Houghton Mifflin, 2006.
Elphick, Chris, John B. Dunning, Jr. and David Allen Sibley. The Sibley Guide to Bird Life and Behavior. National Audubon Society. New York: Knopf, 2001.
Holland, Mary. Naturally Curious. North Pomfret, Vermont: Trafalgar Square, 2010.
Kroodsma, Donald. The Singing Life of Birds: The Art and Science of Listening to Birdsong. Boston: Houghton Mifflin, 2005.
Stokes, Donald W. and Lillian Stokes. Stokes Guide to Bird Behavior Vols. 1-3. Stokes Nature Guides. Boston: Little, Brown, 1976.