You've heard it since the day you were born - a plethora of voices singing outside. Even in New York City, doves coo and falcons screech while we go about our business. Have you listened? Heard it in your mind and heart? Felt it deep in your gut? Ever wondered what's really going on out there in the palo verdes, gardens, parks or palm trees?
A bird song is a consistently repeated pattern of tones. All other bird vocalizations are called calls. Songs are heard in nesting season. Calls are heard year round. Birds use both songs and calls for communication. For the most part, the boys form the choir. Unlike our prattling species, a bird sings for a reason. He lets others know where his kingdom is and issues no trespassing alerts. He has a biological imperative to find a mate so love songs are in order. Song also helps keep a monogamous pair together once the young make their entrance. While most females do not develop as rich a voice as their mates, cardinals are one exception. The female often sings as well as her mate. They practice a form of duet, called antiphonal singing. Sometimes the alternating, but dissimilar, songs of the male and female Cardinal are so perfectly timed that our ears hear it as one long avian aria.
Like all vocalizations, bird song is produced by syrinx, a structure much like our voice box, located at the bottom of the windpipe. But birds also produce sounds by using their tail, bill, wings, etc. The Common Nighthawk flutters around at dusk and every now and then utters a soft rasping peent... Then, in the checking a quick downward dive, it allows the air to rush through its wings and makes a sound you can imitate by blowing across the mouth of an empty jug. Woodpeckers pound on trees, houses, cooler vents or anything that resonates to attract a mate. While musical talent varies from species to species, and from individual to individual, very few birds fail to make any sound at all, be it a true song or a substitute sound.
Most birds break into full song when they have established their home range. The song slacks off for the very short mating period, often vigorously returning for nest building, egg laying and incubation. When the young are being cared for, the singing diminishes. Unless the pair lays a second clutch, singing stops by the time of the end of the nestling period and the postnuptial molt. Among the birds that resume singing after molting, the songs are far fewer in number, and may be incomplete. Winter signals the end of bird song, with a few exceptions like the Cardinal that pretty much sings the year round.
Ever seen a Curved-billed thrasher giving a concert from atop an ocotillo? Many males attract attention by singing while perched in a conspicuous spot. Often times the same bird advertises time and time again from the same spot or spots. Some birds sing while flying. Larks, bobolinks, buntings, and other small birds rise high in the air over sunny fields or woodlands. They do not flap around, but seem to float above the ground on trembling wings, all the while bursting out in wildly sweet songs. The American Woodcock spirals upward on whistling wings, then chippers away during an abrupt descending zigzag pattern. The combination of a song and visual display increases the chances to be noticed, and thereby mated.
Usually birds do not sing around their nests. When approaching the nest, the male is inclined to be silent, or to use a muted voice. There are reports of the male Black-headed Grosbeak singing while incubating eggs and brooding young. His voice, though much softer than when away from the nest, can still be heard for several hundred feet. Ornithologists have located nests by listening for this song. A few male and female birds sing a quiet, inward whisper song that can be heard no more than 20 yards away. Female mockingbirds, American goldfinches, Catbirds, Warbling vireos, Rose-breasted grosbeaks, and black-headed grosbeaks contentedly whisper while sitting on eggs or young. Sometimes whisper songs are heard when birds are alarmed or in rain, often in the cover of trees or shrubs.
All singers have to learn their craft by practicing. Birds often begin their vocal life with a subsong - a random subdued warbling with recognizable call notes scattered throughout. The young male songbird next adds some notes to the mix of warbling and call notes that suggest his adult or primary song. The subsong grows more varied, and by his first autumn, the young male is singing his rehearsal song. By the next spring, the bird has gradually dropped the random warbling and call notes and is singing his adult primary song. The primary song is composed of repetitions of short motifs or sequences of notes in a definite pattern. Once established, the motifs remain largely unchanged throughout the bird's life. Some birds, like wood warblers, have secondary songs that are as complex as their primary songs.
Birds generally sing more in the early morning and late afternoon. The amount of light has more influence on the beginning and cessation of singing than the time of day. Clouds delay the onset of song in the morning and hasten its end in the evening. Not all birds require the same amount of light and dark to stimulate singing, and consequently, also depend on specific amounts of light and darkness to trigger their songs. Total solar eclipses result in a dramatic demonstration of the effects of light and dark upon bird song. As the world grows darker, the diurnal birds ceases singing as they would at twilight. Then the crepuscular birds, those that are active at dawn and twilight, join in. As totality comes on, the nocturnal species add their voices as well.
Finally, the concept of birds singing for the joy of it can't be entirely ruled out. Here's how Thoreau saw it: