the song of birds -- 7/1/20
Today's selection -- from The Bird Way by Jennifer Ackerman. The songs of birds, and the purposes of those songs, are seemingly infinite. Some birds start to learn songs while still in the egg:
"Bird songs and calls range from the odd comical cluck and rattle of the willow ptarmigan and the soft piping voice of the pardalote, barely audible, like whispered gossip, to the elfin chucklings of Leach's storm petrels, the gongs of three-wattled and white bellbirds, the loud trumpeting of the southern screamer, the organ-like caroling of Australian magpies, and the gorgeous, haunting nocturnal solo of the pied butcherbird, which may go on for seven hours. Butcherbirds are the Sweeney Todds of the bird world. They do dastardly deeds -- skewering small birds and other animals for dinner -- but they sing like seraphim, sometimes in trios. So spectacular and haunting is this bird's song that violinist and composer Hollis Taylor worked for a decade recording it and transforming it into music. In 2017, the striking composition she created incorporating her field recordings, 'Taking Flight,' was performed by the Adelaide Symphony Orchestra.
|Australian magpie - Click here to hear it sing|
"Among the weirdest calls I've ever heard comes from the green catbird, a handsome little bird with such perfect camouflage, a mottled green and fawnish brown, that it's more often heard than seen in its rainforest home. Its call sounds like a cross between a yowling cat and a wailing toddler. The first time I heard it, I thought, 'What in the world is happening to that poor child?'
"Science is just beginning to parse the complexity and meaning of bird vocalizations. Even common species such as American robins make more than twenty different types of sounds, most of which remain mysterious in purpose. The simple honk of a goose, it turns out, contains unexpected richness and intricacy; and calls that sound simple and uniform, such as those of penguins, vary in their acoustics, helping penguins recognize one another and choose mates.
"The vocalizations of most songbird species differ from place to place, forming local 'dialects' just like human accents, distinct and long-lasting regional and cultural differences in the structure and composition of songs. These dialects play a role in courtship -- females of some species prefer males with songs that include syllables from their own song vocabulary -- and also, in resolving territorial disputes, allowing birds to distinguish between local and foreign individuals and settle conflicts without fighting. The ornithologist Luis Baptista was among the first to recognize bird dialects in his studies of the white-crowned sparrow in coastal California. Called the 'Henry Higgins of the bird world,' Baptista could pinpoint the geographic origin of a sparrow and its parents just by listening to its song. So localized were the accents of these birds, he said, that one could stand facing the Pacific and hear the songs of one dialect with the left ear and a different one with the right.
"The voice box of birds is a structure called a syrinx, buried deep in a bird's chest cavity. Sound emerges when the membranes of the syrinx vibrate, shifting the flow of air through the organ. The syrinx in birds varies from the bulbous resonance chambers and long looping trachea of ducks, geese, and swans -- up to twenty times the expected length -- which produce sound that exaggerates their body size, to the tiny pair of chambers in songbirds, controlled by delicate syringeal muscles. Some songbirds have such fine control over the multiple muscles in both sides of their syrinx that they can produce different sounds at the same time, in essence, singing a duet with themselves. This accounts for the rich caroling of the Australian magpie and the glorious fluted warbling of the wood thrush.
"It was once thought that the hearing of birds was limited to a smaller frequency range than human hearing. Only lately have we learned that some birds such as the vinous-throated parrotbill and the black Jacobin hummingbird make sound in the ultrasound range, beyond human hearing, suggesting they may also be able to perceive sounds 'invisible' to our ears. Birds are generally better at recognizing sound than we imagined, keenly sensitive to variations in pitch, tone, and rhythm in the sounds of their own species, which allows them to identify fellow birds not just as members of their own species, but as individuals within their flocks, even in noisy, chaotic conditions.
"A fine example of birds using sounds to recognize individual members of their own flocks: the contact calls of budgerigars, which vary subtly from one bird to the next. Like queleas, budgies live in huge flocks. There was a time, in the 1950s and 1960s, when the birds were described as 'so thick on power lines that the wires sagged nearly to the ground with their weight.' Their contact calls allow them to identify their mates and their flock. They can continue changing these calls as adults, modifying them to match their mates or other flock members as the birds move from one social group to another.
"Budgies and other birds learn their songs and calls through a process very similar to the way we learn to speak. It's a process of imitating and practicing called vocal learning, and it's extremely rare in the animal world. Vocal learning in birds begins early, just as it does in humans. By the last trimester of pregnancy, a human fetus can memorize what it hears from the external world and is especially sensitive to melody in both music and language. This appears to be true for some birds, too. The embryos of certain species can hear through the shell of the egg; in response to the voice of a parent, their heart rate increases. As a defense against brood parasites, superb fairy-wrens learn special vocal passwords from their parents when they're still in the egg. Scientists have found that at least five days before they hatch, the unborn fairy-wren chicks learn to imitate the call. Zebra finch parents can tell their young while they're still developing in the egg that it's hot outside. This is vital information for a growing chick. In hot climates, birds need to be able to lose heat, which is easier with a smaller body. When zebra finch parents are breeding in a hot climate, and the nest hits a temperature above 80 degrees Fahrenheit, they'll chirp the news to their unborn chicks in the last third of the incubation period -- the moment when the embryos are developing their temperature-regulation system. In response to these 'hot calls,' the chicks will actually curtail their growth and emerge smaller -- an adaptive advantage in the heat.
"Birds cry like children, grunt like pigs, meow like cats, and sing like divas. They speak in dialects and carol in pairs and choruses. They glean all sorts of information from calls and songs -- a singer's species identity, its geographic origin, group membership, even its individual identity. And they use sound in ingenious ways -- to share information, negotiate boundaries, and influence one another's behavior."