Identifying Bird Songs, Calls, and Sounds
A terrific story about Roger Tory Peterson suggests that ears are as useful as eyes in bird identification.
Once, out with a birding expedition and unwilling to get out of bed on a rainy morning, he lay comfortably, half-awake, listening. When the rest of the party came back, soaked but satisfied with their count, Peterson gave them his list—forty-two species, more than any of the others! (A World of Watchers, p. 201)
A bird's song or call is often a birder's first clue to the small creature's presence. By pursuing the unknown singer, birders familiarize themselves with its song and habitat. Listening attentively, they will learn to distinguish a bird by its song.
Birds’ communication is a vital aspect of nature's music that we can enjoy without understanding. But, of course, we want to understand! Despite science and technology, our understanding of communication between birds is still fairly rudimentary.
Experiments have shown that birds’ language is not unlike human language. Birds can be born with their own distinct “tongue,” but more often they learn it from their parents. Each species has its own sound repertory, but with considerable variation. Repertories vary by time of day, season, and circumstances. There are even different dialects for birds of the same species in different areas!
These sounds relay information that identifies a bird to others of its species. Birds can have more than twenty different sounds that they use to communicate with their own species, other species, and even predators.
Recognizing utterances from this repertory helps identify the bird. Although it is often much easier to hear a bird than see it, it is difficult to practice recognition unless a bird repetitively vocalizes.
Harz Mountain Roller Canaries
These canaries are so called for their ability to hold and roll a single note of song. Bred primarily in the Harz mountain region of Germany, Harz mountain rollers are raised as divas. When young birds first begin singing, they are placed in darkened boxes near expert adult songsters. They are cultivated for 13 distinct sounds—eight song tours and five song rolls. Trainers also use recordings and nightingales to help the rollers perfect their repertory.
Ornithologists divide bird vocalizations into two categories, songs and calls. Presently, we believe birds, usually male birds, broadcast songs (also called primary songs) to establish territory and attract mates. Generally, birds sing most in the early morning, less at midday, then resume in the evening. Singing increases in spring until it peaks in about mid-summer. Listen carefully to bird songs and you will find that they rarely last longer than five seconds per song. Similar to the primary song, but shorter and/or softer, are subsongs, whisper songs, and muted songs.
Of all birds’ voices, the nightingale's is the most admired. It is a complex aria, much loved but difficult to describe. The nightingale sings both during the night and during the day; perhaps because other birds are quieter at night, we most identify the nightingale with night. Poets often attribute the song to females, but—like other songbirds—it is always the male that sings, to announce his territory, in the spring.
We do not have nightingales in North America. Nightingales are abundant in southern Europe and range north into the northern Urals, east to Iran and south into Africa.
Despite its showy voice, the nightingale is a drab little bird, reddish brown above and grayish white beneath.
Bird songs have five characteristics—pitch, duration, volume, rhythm, and phonetics. In A Guide to Bird Songs, Aretas Saunders describes a method of making notations of bird songs using lines, dashes, squiggly lines, and words. Traditionalists believe this nonmechanical method refines a birder's listening.
Song-making is strongest among Passerine birds, but certain other birds have other vocal sounds that seem like songs. Mourning Doves coo. Gulls squawk. These, technically, are calls rather than songs. Calls and other sounds communicate about feeding, danger, longing, keeping together during migration, and other such information. Whereas only males sing, both sexes call. Calls are usually shorter—no more than four or five notes—and far less complicated, although they may linger in duration. Contact notes say, “Here I am. Where are you?” Birds of the same species often utter contact notes at the same time, which keeps the flock together. Flight calls roust birds of the same species to fly.
Bird acousticians use sound pictures called spectrograms to analyze bird sounds by their components. Once recorded, the sound registers as a frequency on a spectrograph. The higher the pitch, the higher the frequency it records. (As a reference, middle C is 256 cycles per second. Humans can hear only up to 20 kilocycles per second.) Bird vocalizations range up to 8 kilocycles.
Instead of vocal cords, birds have a special organ at the base of their windpipes called a syrinx. Its two resonating chambers have elastic membranes that vibrate. As air passes through, specialized syringeal muscles modify air pressure from the lungs and vary the sound's volume and pitch. The more muscles a species has, the more complex its song. Several species are such good songsters that they can mimic the songs of other birds. The starling, for example, has been known to reproduce over thirty species’ vocabularies (Bird Behavior, p. 116). Birds can sing while carrying food or even with their bills closed!
Nonvocal bird sounds make fascinating listening. Various species use their wings to produce sounds. For instance, nighthawks dive at great speeds. When air passes through stiffened feathers, it makes a singular noise. Ruffed Grouse flap their wings to make a thundering sound. Ring Doves clap their wings. The Sharp-tailed Grouse rattles its tail quills. Woodpeckers, of course, peck on hollow limbs. When flying in the dark, swifts use “clicks” made by their bills to determine location. Foot-stomping and bill-rattling are other examples.
Other than the birdsongs we are all familiar with, it is difficult to identify the song or call of a specific bird. One way to achieve proficiency is to compare what you hear to bird recordings. Practice is key. Play the recordings repeatedly and compare similar songs. While the dialects may differ slightly with the voices you hear in nature, the characteristics will be recognizable.
To augment the audible differences between species, pay attention to where a bird is and what it is doing when it sings, calls, or makes other sounds. Some sing from the air or on the ground. Others seek out the tops of trees or cling to stalks of lower plants. Some species—especially bright-colored ones—sing from a sheltered place to avoid being seen by predators.
Different postures, such as erect plumage or spread wings, reinforce a bird's communication. Learning to associate sound with the behavior a bird demonstrates when singing or calling helps bird identification. To pinpoint a bird and learn its riff, concentrate on one sound at a time and trail its source until you establish identity.