Of Extinct Rebuilding the Socorro Dove Population by Peter Shannon, Rio Grande Zoo Curator of Birds

B BIO VIEW Curator Notes From the Brink of Extinct Rebuilding the Socorro Dove Population by Peter Shannon, Rio Grande Zoo Curator of Birds In terms of conservation efforts, the Rio Grande Zoo is a rare breed in its own right, using its expertise to preserve and breed species whose numbers have dwindled to almost nothing both in the wild and in captivity. Recently, we took charge of a little over one-tenth of the entire world’s population of Socorro doves which have been officially extinct in the wild since 1978 and are now represented by only 100 genetically pure captive individuals that have been carefully preserved in European institutions. Of these 100 unique birds, 13 of them are now here at RGZ, making us the only holding facility in North America for this species and the beginning of this continent’s population for them. After spending a month in quarantine, the birds arrived safe and sound on November 18 from the Edinburgh and Paignton Zoos in England. Other doves have been kept in private aviaries in California, but have been hybridized with the closely related mourning dove, so are not genetically pure. History and Background Socorro doves were once common on Socorro Island, the largest of the four islands making up the Revillagigedo Archipelago in the East- ern Pacific ocean about 430 miles due west of Manzanillo, Mexico and 290 miles south of the tip of Baja, California. Although the doves were first described by 19th century American naturalist Andrew Jackson Grayson, virtually nothing is known about their breeding behavior in the wild. The reasons for this bird’s dramatic decline are complex. In 1869, sheep were introduced onto Socorro Island, resulting in slow degradation of the dove’s lowland habitats; currently, the southern part the island shows severe signs of overgrazing, including loss of plant cover, A studbook for Socorro doves is now maintained at the Frankfurt presence of exotic or introduced plants and lack of seedlings or saplings Zoo and based on these data, the population is periodically analyzed from native plants that play an important role in maintaining the natural regarding its genetic and demographic status. Breeding recommendations vegetation. In 1957, the Mexican navy set up a permanent military base and transfers of doves are coordinated through the studbook keeper on the island which brought not only people, but cats, which probably and affect all 22 European zoos currently participating in the program. had a serious negative impact on the dove population, as well. The decision to move pure Socorro doves to the U.S. was made for Fortunately, this particular species was saved from total extinction, several reasons: thanks to a group of foresighted individuals who took part in a California Academy of Science expedition to the Revillagigedo Islands in the 1920s • To establish a satellite population outside of Europe in case Avian and preserved a number of indigenous birds by bringing them back to Influenza (or any other infectious disease) might affect future efforts to California. The offspring of these birds were later shared with private move birds into Mexico for reintroduction. aviculturists in both the United States and Europe and even though pure lines of Socorro doves eventually disappeared in the U.S., a breeding stock • To free up space in European collections and facilitate expansion of that stemming from those imported into the United Kingdom was continent’s dove population. maintained over several decades by private aviculturists in Europe. The • To form the basis of a breeding population on the North American German Interest Group for Wild Pigeons and Doves began an informal continent. breeding program in the late 1980s, and in t1995, this informal program • To give a strong signal to all the Mexican authorities that the Socorro was turned into an official European Endangered Species Programme dove community on both sides of the Atlantic is strongly committed to (EEP) under the auspices of the European Association of Zoos and the reintroduction project and is prepared to deliver captive-bred birds Aquaria (EAZA). to their indigenous home when the necessary preconditions are met. 1 BIOSCAPE • SPRING 2009 Spring 2009 • BIOSCAPE 1 BIOSCAPE MAGAZINE From England to Albuquerque It’s a great beginning, but we’re still learning as reared doves from our newly-established U.S. we go. Even though the experts in Europe have population will be sent there to establish yet The process of moving birds to the U.S. seen it all, breeding these doves is a new thing another breeding group whose offspring will required months of planning on both sides of for us. be released directly into the wild. We don’t the Atlantic. The EEP coordinator identified know yet if it will take one year, five years 12 birds (six males and six females) from the Going Back Home or even more, but we here at RGZ are Edinburgh and Paignton Zoos in England as the committed as the holders of this unique species to do everything in our power to keep best candidates for this transfer, after which The ultimate goal of all of this work, of course, it from disappearing from the earth altogether... the group was put into isolation and screened is to one day return doves to Socorro Island that’s part of what zoos are all about and it’s for medical conditions. Meanwhile, all institu- and help re-establish the ecological balance why we come to work in the morning. tions applied for the necessary permits that of that region. Currently, the Mexican would allow the birds to travel. government is preparing the way by removing sheep and cats from the island; the Mexican With all the paperwork in place, the 12 birds navy is working to restore habitat; and the were loaded onto a British Airways flight on Island Endemics Foundation and Endemicos October 16, 2008 and arrived in Los Angeles the Insulares have already built a state-of-the-art next day. From there, they were transported to breeding station on the island. the United States Department of Agriculture’s quarantine station in San Diego and isolated for “Extinction is forever,” and this holds true the required 30 days. After no problems arose not only for the large and attractive birds and during this quarantine, the birds were trans- mammals that often capture our attention so ported to RGZ on November 18. readily, but also for the many small, but ecologi- cally-no-less-important plants and invertebrate Because ours is a new program, we currently animal species around the world. Although the have the least valuable birds, genetically speaking, endemic elf owl has already become extinct so that we can refine our breeding strategies and on Socorro Island, our restoration efforts with get the population going; however, once we’re the doves will also help other bird species more established, we’ll get a second importation including the Socorro mockingbird, the with a better mix. Socorro parakeet, and the Townsend’s shear- water. Our work is an effort to forestall Reproductive Learning Curve further extinctions of Socorro Island species, and reintroduction of the doves will Socorro doves are typically maintained as help balance and strengthen the island’s pairs and require only a simple diet of seed, ecosystem as a whole and promote protection chopped fruit and vegetables. They can be of the coastal sea habitat around it. very aggressive and need a highly structured The Rio Grande Zoo is the only North American captive environment with multiple potential nesting Once the threatening environmental issues breeding facility for Socorro doves, a species that has locations and places to get out of sight in on Socorro Island are resolved, the captive- been extinct in the wild since 1978. order to breed and rear their young success- fully. Additionally, we make every effort to allow the birds the opportunity of selecting their own partners which establishes compat- ible pairs and further increases their chances of reproductive success. The new aviaries under construction at RGZ will encourage this type of nesting behavior. Shortly after arriving in Albuquerque, one breeding pair became established and began laying fertile eggs while still in quarantine at RGZ! When young birds with no breeding experience start to nest, they often don’t know what to do, and as a result, this pair abandoned the first two clutches early in the incubation process. A third clutch, however, resulted in the hatching of one live chick on January 5 which fledged from the nest late in the month. The pair recycled and another chick hatched on February 4. 2 BIOSCAPE • SPRING 2009 Spring 2009 • BIOSCAPE 2.

Load more