National Park Feature Articles
Bird songs and soundscapes
by Michael Morris, Mount Revelstoke and Glacier National Parks
May 28, 2003
Nothing heralds the arrival of spring quite like the sounds of birds and I try to keep up with the stream of newly returned bird species to Columbia Mountains. Week by week, the morning soundscape grows in volume and variety, serving up the audio jewels we’ve missed all winter.
Bird watchers may be known for the binoculars hanging around their necks, but due to the dense vegetation of this region, I prefer to keep track of the bird world more by listening than by looking. Bird sounds distinguish species better than any other trait.
Increasing day length stimulates the production of the hormones that drive male birds to sing. They sing through the spring and early summer to establish territories and to attract mates. A female bird evaluates a male bird’s desirability as a partner by a careful examination of his vigour, usually expressed as bright plumage or the quality of his song. A male must be a successful forager to have enough energy to grow bright new feathers or to sing constantly during the spring courtship period. Brightly feathered male birds use appearance to intimidate rivals or catch the attention of females. In contrast, the muted plumage of some female birds seems intended for camouflage. Bright feathers or singing must make males much more susceptible to predation.
All bird species have calls unique to their own kind, which they know when they are hatched. Alarm calls signal danger and location calls keep families or flocks in contact with each other. Generally, the birds with the elaborate songs belong to the least conspicuously coloured male birds.
Dr. John Woods and his sound recording equipment. Michael Morris photo
The most spectacular group in this regard are the songbirds -- warblers, thrushes, wrens, robins, vireos, finches, sparrows, and many others. Most songbirds are but temporary visitors to Canada, making a long journey from the tropics to nest and raise chicks here because of our season of abundant insects. Most cease the effort of singing by mid July, once the young of year have fledged.
Humans vocalize using our larynx, which uses about 2% of exhaled air. The corresponding structure in birds is the syrinx. It’s vastly more efficient using nearly all the air that passes through it. And because it has two tubes, each with its own set of sound producing membranes, birds can express two sounds at once, in effect singing along with themselves. Or they can catch small breaths through one tube while singing.
Complex vocalizations also require sufficient mental capacity. Relative to their body size, birds have larger brains than any other vertebrates except mammals. Male white-crowned sparrows learn songs from their father and from other males in the vicinity. They try to match the other songs in their neighbourhood but slight variations emerge to create regional dialects. Some species, like song sparrows, have extensive individual repertoires, that is, they have multiple versions of the song they use to show off to females and to impress less capable males. What with 31 subspecies of song sparrow in North America, each with a slightly different repertoire of songs, bird song recognition is a challenging pastime. Each spring finds me referring to bird identification CDs and my personal recordings to refresh my memory. Because of regional variations in songs within a species, the more local the recording the easier an identification can be made.
Winter is a less confusing time to start to learn bird sounds because there are fewer species to sort out. As spring turns into summer and the more distant migrants from South America arrive, the number and complexity of sounds in a dawn chorus becomes pleasantly overwhelming. As the season progresses, listen to how the soundscape develops over time in your own yard. Because birds specialize to particular habitats, the soundscape of a single morning will vary with elevation. The Meadows in the Sky Parkway on Mount Revelstoke is an easy place to check this out as spring advances up the mountainside from April to July.
Soundscapes
Sound is so much a part of our world that we often ignore it. Computer fans, furnaces, refrigerators, fluorescent lights, passing vehicles, train whistles, lawnmowers, chain saws, and so many other mechanical sources of noise have conditioned us to tune out. In those increasingly rare places quiet enough to hear natural sounds, many of us lack the skill to know just what it is we are hearing. Park visitors frequently ask us to identify a bird song they have heard but we have difficulty understanding their description of the sound. In comparison to the range of words we have to describe what we see, we lack vocabulary to discuss what we hear. Test your own skill at describing a particular bird song to someone else.
To help us out, the Friends of Mount Revelstoke and Glacier sponsored the production of a CD, “Discovering Birds and Their Songs in Mount Revelstoke and Glacier National Parks.” It points listeners to where and when to hear the key birds of our wetlands and forests, using local recordings. Paying attention to birds, while interesting in itself, is but half the treat. Tuning into the natural soundscape opens us to all that peeps, squeaks, hums, buzzes and crackles in the Columbia Mountains. Contact the Friends at fmrg@telus.net.
Click to hear Michael’s recordings:Black-capped Chickadee (25 KB MP3 file) Swainson’s Thrush (76 KB MP3 file) |
Anyone with patience and a moderately priced cassette deck can collect sounds. Minidisk recorders work even better. However, the keys to the creation of a good sound clip are a quality microphone and a quiet background. Of the many styles of microphones, the most common for this purpose are: the shotgun mic, the kind used by TV news reporters, which is very directional and aimed at the sound source; and the omni-directional mic, which gathers sound in all directions equally. An omni-directional mic mounted in a parabolic dish can isolate sound even better than a directional mic. Recordings are played back into a computer by way of a simple cable for editing. What used to require an elaborate sound-editing studio can now be handled with inexpensive computer software.