A fascination with the diversity of life has led Stephen Pruett-Jones again and again to ask, “Why?”

In bright green wingtips, they stand out among the more subdued hues favored by University students. They often screech during summer mornings near the David and Alfred Smart Museum of Art and pick berries off the quads' holly trees in the fall. They are monk parakeets, and they are more than the stuff of campus legend.

Known for his own colorful Hawaiian shirts, Stephen Pruett-Jones, associate professor in ecology & evolution, the Committee on Evolutionary Biology, and the College, has embarked on the first major biological and ecological study of America's monk parakeet population. He wants to know whether the monk parakeets-regarded as agricultural pests in their native South America-could harm crops in Illinois and how they survive the harsh Chicago winters.

Working out of an office that comfortably accommodates a border collie named Mik, vases of bird feathers, and an inflatable southern hairy-nosed wombat, the 45-year-old zoologist says such questions follow his broader line of inquiry into the evolution of animals' social behavior and their mating systems. He also plans to expand this year his ongoing studies of the mating rituals of the Australian fairy-wrens and of the dark-winged damselfly.

But Pruett-Jones says he couldn't resist studying the monk parakeets, given their campus proximity and lack of academic attention. The first sighting of Chicago's free-flying monk parakeets dates to 1973. According to local lore, they settled in Hyde Park after escaping from a cage at O'Hare International Airport. That rumor may be based on a documented escape at a New York airport, Pruett-Jones says, suggesting that the Hyde Park population more likely sprang from the escape or even intentional release of pet monk parakeets, which, unlike some other small parrots, have poor mimicking skills and high-pitched screams. Adding to the birds' legend, the late Mayor Harold Washington is said to have directed police to protect the colorful creatures that flew outside his apartment overlooking "Parrot Park" at Lake Shore Drive and 53rd Street.

Today, Pruett-Jones estimates, Hyde Park's monk parakeet population has grown to about 200, with 80 nests perched on power transformers and in the trees of Parrot Park and of Washington Park. He predicts they will be flying all over the continental United States within the next two decades. So far-in at least six other states, including New York and Florida- they have inexplicably chosen parklands, suburban lawns, and backyards with birdfeeders over croplands. "I previously thought the monk parakeets should be controlled because an introduced species is almost always bad for its new environment," Pruett-Jones says. "But now I believe they are sufficiently benign in the habitats where they now occur. They're not a pest, and they don't compete with a native species."

With the mysteries of the monk parakeet awaiting him, Pruett-Jones, who holds a Ph.D. in zoology from Berkeley, returns this month from a field study of his primary winged subject: the Australian fairy-wrens. For six weeks, he has been tracking and observing the tiny birds-weighing just 10 grams each-in Brookfield Zoo's Brookfield Conservation Park, located 100 miles northeast of Adelaide in southern Australia.

For the past seven years, Pruett-Jones has studied one particular species-the splendid fairy-wren. He was initially struck by the contrast between the dull brown females and the brightly plumed males who look "like little blue gems." He also wanted to get to the bottom of why male and female fairy-wrens raise young with one partner while continuing to mate with others. He seeks to scientifically answer the age-old question: "Why would it be an advantage to be socially monogamous but sexually promiscuous?"

To do so, Pruett-Jones and his assistants typically spend three months in the field each year. They band the birds, record their height and weight, and collect blood samples. Covering three square miles, they also map the birds' territories and observe their feeding patterns and mating rituals. Back at the U of C, Pruett-Jones and his team then spend another nine months in the lab analyzing the blood samples using DNA "fingerprinting." These samples hold the real keys to the "discreet" birds' behavior, Pruett-Jones says. While the team may be able to observe a single bird copulating as many as ten times during the course of a field study, the DNA analysis tracks the thousands of such liaisons actually engaged in by the bird and any resulting chicks.

Although Pruett-Jones has concluded that all female fairy-wrens engage in "extra-pair copulations," with most raising their young with the support of a "helper" male, he cannot yet explain exactly when and why they do this: "My hunch is that group living and family life are important to avoid predators and that the females may not always be paired with the most desirable reproductive males."

On this fall's trip to Australia, the team planned to study white-winged fairy-wrens, a species Pruett-Jones says raises even more interesting questions. The male and female white-winged fairy-wrens, he explains, look alike until age 4, when the genders can be distinguished by changes in plumage color. During those first four years, females sometimes mate with female-looking males. "I think the females are mating with the look-alikes because the look-alikes provide better parental care and are the better fathers," he speculates. The switch to white-winged fairy-wrens also gives Pruett-Jones the chance to be the first to explain the independent evolution of two variations of the species on two islands off the western coast of Australia.

Yet another winged creature has flown into the project files of Pruett-Jones. This past summer, he taught at the University of Michigan's Biological Station on Douglas Lake-in the northern tip of the state's Lower Peninsula-where he began a study of the mating rituals of the dark-winged damselfly. He examined, in part, whether the damselflies pay attention to the symmetry of each other's wings when looking for a partner. "Evolutionary biologists have found that individuals in societies are sensitive to asymmetries," he explains, and, indeed, he found that female damselflies do tend to favor the more symmetrical males. He now wants to find out whether the females favor the symmetrical males because they're more attractive or because they can better defend their territory.

Although such discoveries may not apply directly to humans, Pruett-Jones notes, "they help us learn about ourselves. We're all connected to animals." And they affirm the excitement of his work. "Many aspects of diversity in the animal kingdom relate to diversity in mating systems," he says. "The exaggerated tail of the peacock, the bullfrog's call, why birds sing-all of the enormous diversity of life relates to reproduction."-C.S.