All the text and photos by Simba Chan (BirdLife International)
The audio-visual social attraction of Chinese Crested Terns at the Jiushan Islands had a second and even more successful year: at least 43 Chinese Crested Terns arrived and stayed on the island of Tiedun Dao this breeding season (from mid-May to early August 2014), and at least 20 breeding pairs formed. In early August at least 13 young Chinese Crested Terns fledged. For a species with a previously known global population of not more than 30 birds (current estimated global population not more than 50 individuals), this is a remarkable, almost miraculous, success.
Chinese Crested Terns were presumed extinct in the late 20th century. This species was rediscovered at the Mazu Islands along the coast of Fujian Province in 2000, and one new colony was discovered at the Jiushan Islands, Xiangshan County of Zhejiang Province, in 2004. Because of illegal egg collection, however, the terns ceased to breed on the Jiushans after 2007 and the colony apparently moved to the Wuzhishan Islands in the same province.
Since 2011, BirdLife International and the Hong Kong Bird Watching Society (BirdLife in Hong Kong) have been working with Zhejiang Museum of Natural History, the Zhejiang Wild Bird Society, the Ocean and Fishery Bureau of Xiangshan County, and a team of tern experts from Oregon State University in the United States on a restoration project for Chinese Crested Terns in the Jiushan Islands, using the audio-visual social attraction methods of decoys and playback of tern calls developed by Dr. Stephen Kress, Vice President for Bird Conservation at the National Audubon Society (BirdLife in the USA). Dr. Kress observed that “the results of the summer demonstrate how dedicated biologists can make an enormous difference for saving species by taking direct action at the right place and time. The results of this past summer offer new hope for the most endangered seabird in the world.”
The restoration work started during the breeding season in 2013. The first year was extraordinarily successful, but the new colony got a late start compared to the normal tern breeding season. To make sure that no adverse factors affected the nesting terns in 2014 and to record the breeding behavior of this poorly known species, a simple monitoring station was built on Tiedun Dao, the 2-hectare island chosen for breeding colony restoration. Simba Chan, Senior Conservation Officer of BirdLife International Asia Division, stayed on the island from 8 May to 8 August to monitor the tern breeding colony and the threats to successful nesting: the most serious predators on nesting terns were a pair of Peregrine Falcons that visited the colony frequently in June and July. An attempt to poach eggs from the colony (illegal egg harvest) was prevented and a poacher was arrested on 3 June after the poacher was reported to the authorities by the monitors. Three typhoons passed through or near the Jiushan Islands during the 2014 breeding season, but did not cause observable damage to the breeding birds and their young. By the end of the breeding season, a large quantity of data regarding the breeding biology of Chinese Crested Terns had been collected and these data will likely prove very useful for future management and design of additional restoration projects for this critically endangered species.
Based on preliminary observations, Chinese Crested Terns appear to be as highly adapted to the marine environment of southeastern China as the more common and closely-related Great Crested Tern. Chinese Crested Terns are highly efficient at finding and catching forage fish and adapt 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 probably due to their restricted breeding range; as their name suggests, they were only found nesting along the east coast of China. If illegal egg-collection is completely stopped, they have a good chance of recovering and may eventually re-establish their former breeding colonies in Shandong, where the last birds were collected in 1937. Restoration of this northern breeding site may prove to be pivotal for this species, as its current nesting sites in Fujian and Zhejiang are at risk from typhoons during the breeding season.
This year at least 40 Chinese Crested Terns turned up on Tiedun Dao at the beginning of the breeding season. This surprisingly large number suggests that nearly the entire world populations gathered at the attraction site or possibly there is a previously unknown colony somewhere along the coast of southeastern China. Simba Chan does not support this hypothesis. He states, “I am pretty sure we have about 90% of the global population on the island this year: there were no Chinese Crested Terns on Wuzhishan in May and June, and the number in Mazu Islands at the beginning of the breeding season was also lower than usual.” Apparently when the terns arrived on the southeastern coast of China this spring they explored an extensive area looking for suitable breeding sites. Amongst the three to four thousand Great Crested Terns also attracted to Tiedun Dao this season, three birds banded birds in the Mazu Islands were observed, strong evidence that many of the terns attracted to the Jiushan Islands were from the Mazu Islands about 400 kilometers to the southwest. If terns from the Mazu Islands could be attracted to the Jiushan Islands, then the chances of another unknown colony site for crested terns seems low, as crested terns are highly social birds. The audio-visual social attraction has proven to be far more effective than had been anticipated. Up to 90% of all the Chinese Crested Terns in the world may have been attracted to this one-colony site. In addition to the Great and Chinese Crested Terns that are known to breed on the Jiushan Islands, a pair of Lesser Crested Terns also laid and incubated a fertile egg (embryo died before hatching) on Tiedun Dao this year. This is the first breeding record for this species in China.
Although this is an excellent result from the first two years of this restoration project, the Chinese Crested Tern restoration team, is concerned that this critically endangered species should not be so concentrated at just a single breeding site. There are suggestions to improve the nesting habitat and use social attraction at the Wuzhishan Islands and the Mazu Islands next year, with better coordination and management at all three sites. To solve the mystery of the Chinese Crested Tern’s migration and over-wintering areas, a banding project for the Great Crested Terns in the area has also been proposed. Gradually, more will be learned about the biology and migration of the crested terns in eastern China, and these and other seabird populations will be restored with the help of well-designed outreach and education programs. At the 26th International Ornithological Congress (17-24 August 2014, Tokyo, Japan), the Chinese Crested Tern restoration team will chair a round-table discussion on restoration of tern breeding colonies on 23 August. It is hoped more interest on international cooperation and restoration of tern and other seabird colonies will be generated, particularly in Asia, from this project.
This project has been possible through the generous support of the Xiangshan Ocean and Fishery Bureau, the Zhejiang Museum of Natural History, the Japan Fund for Global Environment, the Ocean Park Conservation Foundation (Hong Kong), Endangered Species Fund from the State Forestry Administration of China, Pacific Seabird Group and BirdLife International Preventing Extinctions Programme supporter – Mark Constantine. The two organisations in Zhejiang Province also provided significant logistical support that helped make the project such a resounding success. The U.S. Fish and Wildlife Service (Wildlife Without Borders) supported the project by providing decoys and playback equipment needed for social attraction.
Press release(Chinese): http://www.hkbws.org.hk/BBS/redirect.php?tid=21535&goto=lastpost#lastpost