By Susan Smith
Answers To Go
—
Each week hundreds of people call or visit the San Marcos Public Library to find information. "Answers•To•Go" highlights recently received questions. Please visit the library at 625 East Hopkins, call 393-8200 for information over the phone, or e-mail us through our webpage at www.ci.san-marcos.tx.us/library.htm.
Q. I’m not really a birdwatcher. However, I’m often fascinated by birds that I don’t see in Texas when I’m traveling. Last year, I saw eagles hunting on the coast at Washington’s Olympic National Park. This year, it was magpies in Colorado. Their black and white markings are nearly as dramatic as those of penguins and skunks. I’d like to know more about magpies and their habits.
A. You’re in luck. I’ve got just the book for you — Candace Savage’s “Bird Brains: The Intelligence of Crows, Ravens, Magpies, and Jays.”
This Sierra Club book is clearly a labor of love. Savage balances a layman’s discussion of research with her big, beautiful photos of magpies and other members of the fascinating corvid family of birds.
From “The Audubon Society Encyclopedia of North American Birds,” she cites ornithologist John K. Terres’ opinion that corvids have probably achieved the highest degree of intelligence to be found in any birds.
Savage continues, “By the 1960s, neurologist Stanley Cobb discovered that the avian brain is built on its own unique plan. Instead of relying on an elaborate cerebral cortex, birds have developed another part of the forebrain, the hyperstriatum (which mammals lack), as their chief organ of intelligence.
“The larger the hyperstriatum, the better birds fare on intelligence tests. Crows, ravens, and magpies are all at the high end of the scale. Corvids are also tops among birds for overall brain size. (Their brain-to-body ratio equals that of dolphins and nearly matches our own.)”
Savage admires the magpie’s nest building skills: “A magpie nest is a major engineering feat — a structure composed of perhaps fifteen hundred sticks, cemented together with a layer of mud, and sometimes, cow dung.
“The container is then lined with fine roots and stems, supplemented with bark fibers, hair, and grass. Arching over the whole structure, the birds construct a protective roof of twigs, often armed on the outermost surface with thorny branches.
“One or two openings in the sides let the magpies fly in and out of their fortress. But nest predators, including owls and large crows, find it difficult to breach these defenses, and this is presumably why such elaborate constructions have evolved.”
Savage then turns her attention to fledgling magpies: “As ornithologist Konrad Lorenz and other observers have noted, fledglings often seem pathetically dependent on adult guidance. Young magpies, a day or two out of the nest, go into a panic over a falling leaf yet fail to take cover when a hawk soars overhead.
“Some of them pay a high price for their incompetence. In one study, more than a fifth of magpie fledglings fell prey to owls, hawks, and falcons within two weeks of leaving the nest.
“Biologist Deborah Buitron, who watched the goings-on at more than two dozen magpie nests in South Dakota, observed what she thought might be ‘anti-predator lessons.’
“A whole family of magpies would take off after a coyote or a crow, harassing it with machine-gun blasts of loud, rattling calls. The birds’ alarm calls varied with the degree of danger that the birds perceived.
“If the magpies saw a falcon perched in a tree, they swooped at it with loud, long rattle calls; but if the predator took off—thus posing an immediate threat to its pursuers—the volume and intensity of the call increased to a siren-like wail of staccato shouts.”
“Bird Brains” is just one fascinating, gorgeous example of the library’s books on wildlife for both adults and children. Come on in and check some out!
