Listen to the Mockingbird
Whether belting out a song or belting a rival, nature's master mimic will stop at nothing to win a mate
Samuel Grimes can still remember the first time he heard the song of the mockingbird. "I was five years old, sitting on the porch of my family home in Kentucky," recalls the 80-year-old photographer. "And this bird was in a tree just a few feet away, singing so clear and so close. It amazed me."
Captivated by that memory, Grimes put down his camera two decades ago and picked up a tape recorder. He crisscrossed the country, collecting 45 hours of the sweet song of his favorite avian species. The result was "The Vocally Versatile Mockingbird," a sort of "greatest hits" record documenting the talents of Mimus polyglottos (Latin translation: "many-tongued mimic").
You name it--other bird calls, sirens, bells, frogs, crickets, squirrels, a home alarm, rusty gate, the whirring and squeaks of a washing machine--and this extrovert of lawns and hedges will imitate the sound with grace and skill. Grimes tells of one mockingbird near Miami that mimicked an alarm clock so perfectly that it awakened residents early every morning.
In truth, no other animal on Earth can touch the northern mockingbird, as the North American species is called, when it comes to copying the sounds of its environment. Parrots can be taught to mimic, but only in captivity. Thrashers and catbirds--mockingbird relatives--will get off a good imitation only once in awhile.
So why do mockingbirds mock, anyway? Just who, besides Grimes, is listening? Behavioral researchers believe they have the answer. Mockingbirds apparently sing for the same reason humans turn the lights low and put Frank Sinatra or Luther Van-dross on the stereo.
But while getting in the mood may be mere romance for people, it is essential to the mockingbirds' survival. Scientists have found that fluctuations in the birds' singing coincide strongly with hormonal changes that are necessary for mating and nesting in the spring and summer.
Unrestrained singing by males not only tracks production of their own testosterone, but studies suggest it may also serve to "reset" the female's reproductive system. What's so sexy about imitating the ping of a bell, the scream of a red-tailed hawk or the chattering of a chipmunk? Kim Derrickson, an ornithologist at the Smithsonian Institution, has been studying mockingbirds almost exclusively for several years in Washington, D.C.'s Rock Creek Park. As he explains, "the mockingbird's song is the vocal equivalent of a peacock's tail."
For males, which do all the singing during the breeding season, an elaborate repertoire sends a scintillating message to a female. Life is tough in the wild, where predators, disease and starvation are constant threats. The variety in a male's songbook is a signal to females that he is wise to the world, has survived for awhile and established a territory with plenty of food.
That's important for the survival of not only the female but also of future fledglings. "Male mockingbirds are better fathers than the females are mothers," says Randall Breitwisch, a University of Dayton ornithologist. Males build the nests and provide most of the food for the nestlings. And it is mostly the males, with a little help from females, that drive away cats, jays, snakes and other predators from the nesting territory.
Mockingbirds are unusual among birds in their unrelenting focus on breeding. It's not uncommon for a pair of mockers to carry out the breeding process four or five times in a season, with the loss of a nest to a predator triggering a new outburst of song to start things all over again. While most other North American birds become silent or migrate in the fall, mockingbirds keep on singing in hopes of landing a mate for next spring.
Only in recent years have scientists discovered how adaptive the gray-and-white creatures are among North American birdlife, especially compared with other species threatened by disappearing habitat. The northern variety is one of several mockingbird species found around the world, particularly in the tropics and South America. While originally native to open scrub pine and oak forests of the West and Southeast (there is an eastern race and a slightly larger western race), mockingbirds have recently increased their numbers in the northern part of their range, as they push into previously uninhabited territory.
The key reason is simple: They like what suburbanites have done to huge swaths of the continental United States and southern Canada. "Mockingbirds love mowed lawns and ornamental shrubs," says Peter G. Merritt, a Miami ornithologist who did much of his doctoral work on the species. "These are great places for them to forage for insects and berries. Man has created a habitat to which they were pre-adapted."
The birds' propensity for suburban living has been a boon, not just for them but for people, too. It's the mockingbird's personality, perhaps more than its song, that makes the species so distinctive, endearing and, from time to time, obnoxious. Official state bird of Texas, Florida, Arkansas, Tennessee and Mississippi, the mockingbird "has qualities we admire and talk about," as Texas naturalist Roy Bedichek puts it.
Long before the Europeans came to this continent, the mockingbird's song captured the attention of native Indians, who believed the creature was ridiculing other birds in the forest. One tribe of Algonquins called it Cencontlatolly, or "400 tongues." The Biloxi Indians believed it "mocked one's words," while the Choctaws called it the bird "that speaks a foreign tongue." In Hopi myth, the mockingbird gave the tribe the gift of language.
The mocker was quick to catch the fancy of newcomers to North America. "He imitateth all the birds in the woods . . . [and] singeth not only in the day but also at all hours of the night," observed colonist Thomas Glover in his "Account of Virginia" in 1676. President Thomas Jefferson kept one as a pet. Poet Walt Whitman wrote sadly of a mockingbird near his Long Island home that, Whitman theorized sang all the time because it had lost its mate.
Waxing poetic about the mockingbird is fine--up to a point. Before the advent of air conditioning, it was a rare southerner who never felt the urge to throw a shot or shoe at a lovesick mockingbird at 3:30 on a steamy spring morning. Scientists who have studied the birds say the extended, eleventh-hour singing is exclusively the work of unmated males. Alas, these crooners often become piles of feathers on the lawn the next morning, victims of predators.
Most of the singing stops during the cold months. Then, as winter recedes and the days grow longer, the symphony begins anew, and the medley becomes more frequent and more intricate as spring approaches. What begins softly in February, when the birds prefer to remain hidden in shrubs and evergreens, is by April a sonata with elaborate themes. Males belt out their acquired mimicry as they fly around their territory, hoping to attract a female.
Derrickson, who has analyzed sonograms of mockingbird songs, says there appears to be no limit to the number of songs a mocker can pick up. Most will master at least 180 songs in a few months. But "if you followed a bird for an entire mating season, you would end up with more than 400 song types," he says. "There is no point at which their repertoire flattens out. They just keep adding. Some they will forget or not use; others they will remember into the next breeding season."
A mockingbird's song can match the frequency and timing of the imitated sound with astonishing accuracy. Derrickson has recorded a mockingbird that mastered not only the call of a male red-winged blackbird, but also the paired response of a female red-wing. In other words, the mockingbird was performing a duet with itself. A virtuoso bird can run through its repertoire for almost an hour and repeat itself only occasionally.
Preliminary research suggests that the regional dialects of mockingbirds in the South may be moving northward, passed from bird to bird. According to Derrickson, though, mockers in the North singing the songs of the South may merely be mimicking the calls of migratory species passing through the area.
At first, some students of mocking bird behavior thought mimicry might serve as a kind of defensive gesture, designed to drive away rival bird species. A flock of blue jays flying through mockingbird territory, for example, invariably provokes mockers to mimic and attack. But Derrickson and others now believe the jays simply "remind" the mockingbird that it has already mastered the jay's call.
As soon as a female enters a male's territory, the suitor tries to win her over with a full recital of his repertoire. Once a bond is established, the singing tapers off--if only temporarily. The male bursts once more into song during nesting and breeding, but never more robustly than during copulation itself. Once the eggs are laid, singing declines and another dramatic aspect of mockingbird behavior comes to the forefront--the bird's penchant for guarding its turf.
While the youngsters are under parental care, heaven help any intruder wandering near the fledglings or the nest, which is usually built only 3 to 8 feet off the ground. A few years ago, mail carriers in Houston refused to deliver letters into one neighborhood after they were assaulted by aggressive mockers.
Because mockingbirds don't migrate, establishing territory is essential and plays a major role in their survival. Researchers have discovered that mockingbirds establish two types of territory. One is the spring and summer breeding territory, which a monogamous pair generally holds and defends jointly. While most bird species try to breed once or twice in a season, mockingbirds make as many as five attempts lasting into August. Each attempt begins with a full burst of song by the male that appears to trigger the female reproductive cycle.
Mockingbird pairs, particularly in the northern part of their range, usually split up for the fall and winter. Each bird then may establish a separate, smaller territory around a food source, such as a group of holly bushes or winterberry.
Still, the males sing. Why? Cheryl Logan, a psychologist at the University of North Carolina at Greensboro who has studied mockingbird mating habits, theorizes that the birds "use the luxury of not migrating to get a head start on the mating effort in the spring. They are showing that they can hold a territory, even under difficult conditions."
Logan's research has shown that in the world of mockingbirds, males had better measure up to female expectations--or else. Females that have lost their mates during breeding season have been found sharing "married" males in adjoining territories, moving back and forth from one to the other. Females will also abandon a mate and find another if an attempt at nesting ends in failure.
The mockingbird's charm does not end with its singing ability. While studying mockingbirds at the University of Miami, Peter Merritt was startled to discover that the birds learned to recognize him. They picked him out of a crowd as a familiar intruder and attacked him on sight. Some mockingbirds, in fact, remember intruders from season to season. Kim Derrickson says he has tried wearing a different baseball cap every time he enters the territory of a bird whose nests he has studied. But, he admits, even these clever disguises don't fool the sharp-eyed birds. "They still recognize me."
Cheryl Logan tells the story of one female mockingbird she was observing that spent enormous amounts of time lingering in a campus parking lot. "We couldn't figure it out," she says. "We assumed parking lots were just dead space for mockingbirds." Then she took a closer look: The bird was pulling freshly squashed bugs off car windshields.
In the 1975 Pulitzer Prize-winning book Pilgrim at Tinker Creek, Annie Dillard wrote, "The mockingbird's invention is limitless. He strews newness about as casually as a god." Maybe that's why we all stop, look and listen, as enthralled as young Samuel Grimes was 75 years ago when he first listened to the mockingbird on the front porch of his old Kentucky home.
Lovesick mockingbirds often serenade writer Doug Harbrecht, White House correspondent for Business Week, at his home in Northern Virginia.