By Mark Floyd
CORVALLIS, Ore. – A collaborative project between researchers in Oregon and Asia last year helped establish a new breeding colony for one of the world’s most endangered seabirds – the Chinese crested tern – which then had a global population estimated at fewer than 50 birds.
This summer, at least 43 of the critically endangered birds arrived at the colony on the island of Tiedun Dao in Zhejiang Province, forming at least 20 breeding pairs.
By early August, 13 young birds had fledged.
“It is a remarkable success story,” said Dan Roby, a professor of wildlife ecology at Oregon State University, who helped establish the new breeding colony. “The lessons that we learned in Oregon through luring Caspian terns to new breeding colonies away from the Columbia River translated quite well to the Chinese crested terns.”
Once thought to be extinct, there were no recorded sightings of Chinese crested terns from the 1930s until 2000, when a few birds were rediscovered on the Matsu Islands. Until last year, there were only two known breeding colonies for this species of tern – both in island archipelagos close to China’s southeast coast.
Both of these colonies have been susceptible to illegal egg collection for food, as well as to typhoons that can devastate seabird breeding colonies, Roby pointed out. The effort to establish a new colony was the first step toward creating a network of island sanctuaries where Chinese crested terns and other seabird species of conservation concern could raise their young, he added.
To establish a new colony, a project team including students and faculty from OSU’s Department of Fisheries and Wildlife worked with colleagues in China to clear part of Tiedun Dao of brush, then planted 300 tern decoys on the island and used solar-powered recorders to broadcast vocalizations of both Chinese crested terns and greater crested terns, which are more numerous and not endangered.
“When greater crested terns establish a breeding colony, sometimes it lures in Chinese crested terns as well,” Roby said. “We just didn’t expect it to happen so quickly.”
The China project was designed to recapture the success that Roby and the Army Corps of Engineers had in establishing new breeding colonies in Oregon for Caspian terns far away from the Columbia River, where they had been decimating juvenile salmon migrating downstream. They established new colonies in southeast Oregon and successfully lured thousands of birds to the new sites.
The technique of clearing vegetation, planting decoys and luring birds through playback of vocalizations was developed by Stephen Kress of the National Audubon Society.
Even though the new breeding colony for Chinese crested terns was successful, it wasn’t without peril, according to Simba Chan, senior conservation officer of BirdLife International’s Asia Division, who stayed on Tiedun Dao from early May to early August to monitor the colony. During that time, the endangered birds and their chicks endured attempted predation by peregrine falcons, attempted poaching by an egg collector, and three typhoons.
Chan and his colleagues collected a lot of data about the birds’ behavior that will help inform the management of the birds as well as the design of future colonies.
Chinese crested terns are highly efficient at finding and catching forage fish and adept at defending their nest sites during territorial disputes with their neighbors.
Crested terns breed in very dense colonies with six to seven nesting pairs per square meter. The decline and near-extinction of Chinese crested terns in the 20th century was likely due to their restricted breeding range and widespread overharvest of seabird eggs.
“Having a new, productive breeding site away from the other two known colonies gives the species a far better chance to recover,” Roby said.
The project was supported by numerous international groups.