Image: J. GILARDI, ¿ 1992
Two football-shaped bunches of feathers nap peacefully on a branch inside a low, gray building at the Bronx Zoo in New York City. These St. Vincent Amazon parrots, miles from their natural habitat and oblivious to the plight of their relatives on an island in the Caribbean Sea, live a protected life at the World of Birds exhibit. But private collectors prize such animals¿each might command over $10,000¿helping to create a demand that often outstrips the supply of legally available birds and fuels illegal trafficking. This demand, on top of natural hazards and the St. Vincent Amazon parrot's small range, has put the species at risk for extinction.
Now, in one example of the growing field of conservation genetics, scientists are compiling information that will aid these birds in a variety of ways. Conservation genetics is an umbrella term for a variety of sciences, including ecology, molecular biology and population genetics. It involves the use of detailed genetic information to better manage a species' population and, in many cases, to try to coax it back from the brink of extinction.
Parrots have more endangered species than any other bird family. The St. Vincent Amazon parrot, found only on St. Vincent Island, was first listed as endangered in 1970. The World Conservation Union (IUCN) specified habitat loss, hunting, hurricanes and trade as causes for their decline. "Historic information suggests they were all the way down to sea level on the entire island. But currently they are in a very small chunk of forest left way up in the mountains," says James Gilardi, director of the World Parrot Trust, a charity that works for the survival and welfare of parrots. "So they're sitting on this little remnant of habitat and they've been chased out of the rest of their range and, consequently, they're exposed to more sorts of perturbations in a more severe way."
The parrots' numbers in the wild hit a low point in the mid-1980s, Gilardi says, after they suffered through back-to-back natural disasters: a volcanic eruption followed by a hurricane. The most recent census found higher numbers of wild birds, approximately 800, and IUCN has since reclassified the parrots as merely "vulnerable." Still, that places them at a "high risk of extinction in the wild in the medium-term future." Birds in captivity are spared the hazards facing their wild counterparts. Scientists are trying to increase this captive population, though not for reintroduction purposes. Instead, they want to ensure a healthy, diverse population of captive birds as a reinforcement to those in the wild.
George Amato of the Wildlife Conservation Society and a graduate student, Michael Russello, initially started working with the St. Vincent Amazon parrots when a consortium of parrot enthusiasts on the island approached them with a seemingly simple question: Is there an uncomplicated way to tell which birds are male and which are female? Because St. Vincent Amazon parrots are what are known as sexually monomorphic, it is impossible to tell males from females just by looking at them. Understandably, this led to difficulties in breeding attempts. Many methods of sex determination are invasive, costly and possibly dangerous to the birds, so "[breeders] used to just watch the birds and then remove pairs they thought would be a good match," Russello explains. "In one case, they removed two males and waited for them to breed."
Amato and Russello applied a straightforward polymerase chain reaction (PCR) test to determine the sex of all the captive St. Vincent Amazon parrots living in St. Vincent and Barbados, a total of 79 birds. The simple test required only a feather tip for analysis. It also provided detailed genetic information about the birds that had never been available. According to Amato, the subsequent step in the process was to try to determine how, exactly, the individuals in the captive population were related to one another. With such information now in hand, Amato and Russello hope that it can be used to implement management strategies to ensure a genetically diverse population that is better able to withstand threats to its survival.
Image: J. GILARDI ¿ 1992
One threat that is notoriously difficult to quantify is the illegal pet trade. A recent report in the June 2001 issue of Conservation Biology suggests that earlier analyses have underestimated parrot poaching for the pet trade. "Our results are the first to demonstrate that poaching of nesting parrots is indeed widespread and, in many species, is occurring at levels that probably are not sustainable," says co-author Timothy Wright of the University of Maryland.
The researchers analyzed 23 previous studies of parrot ecology and behavior in the Neotropics¿an area that includes Central and South America, parts of southern Mexico and the West Indies¿and determined that, on average, as many as 30 percent of all parrots' nests were poached. The highest rate of poaching for a single species was more than 70 percent. Island countries exhibited lower poaching rates than mainland countries did. Because parrots have low reproductive success¿a pair will typically produce only one clutch of two or three eggs a year¿some species may not be able to sustain the pressure from such prevalent raids, the authors write.
Because of the St. Vincent Amazon parrot's status, trade of the birds is highly regulated. Would-be owners wishing to import the animals must first obtain permits under both the Wild Bird Conservation Act (WBCA), passed by the U.S. in 1992, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). And only birds bred in regulated captivity can be legally traded.
A byproduct of the genetic research Amato and Russello conducted is a potential tool to stop the smuggling of wild St. Vincents. Because the genetic make-up of the captive, breeding parrots is now known, it is possible to use DNA technology to compile a genetic family tree for their offspring. When a parrot whose origin is in question is confiscated, scientists can compare its DNA to the compiled databank and tell whether the bird was bred in a licensed captive-breeding group.
Amato says that over the course of their studies he and Russello have already uncovered some birds that were said to be products of captive breeding but in reality were not. As he is quick to point out, such a finding could be merely the result of poor record keeping. But it could also be an attempt to launder an illegally caught wild bird through more respectable channels. At the August meeting of the Society for Conservation Biology, Amato and Russello planned to suggest a powerful application for the new technology: that no permits be given for birds moving from one area to another until a feather sample is submitted to verify its pedigree.
Previous examples of the increasing use of genetics for forensic identification in wildlife smuggling have relied on genetic databases¿ such as the National Center for Biotechnology Information's GenBank, assembled for basic research purposes. Amato himself has used such data to determine the origins of contraband caiman skins destined for fashion items and to identify bushmeat confiscated by U.S. customs officials. The St. Vincent Amazon parrot is only the latest threatened animal to benefit from genetic profiling.
Gilardi concurs that the newly compiled data is a powerful tool. "My guess is that it would be effective to nail the people who are coming up with the big money for these birds by pinning them with the genetics and showing that 'Oh, this whole collection is, in fact, full of poached birds' rather than 'this whole collection is full of captive-bred birds,'" he says. "I don't know how much that would deter poachers, but obviously, getting the word out that we've got them all catalogued would certainly help."