Endangered tern threatened by crossbreeding
The Chinese crested tern, the world’s most endangered tern species, could become even rarer because of crossbreeding with a more abundant sister species, Chinese ornithologists have warned.
The hybridization of the two closely related species may erode their gene pools and accelerate the rate of the rare bird’s extinction, said Chen Shuihua, deputy director of the Zhejiang Museum of Natural History.
He said his museum in Zhejiang province and two other institutes collected noninvasive DNA samples from five Chinese crested terns for genetic conservation studies and observed hybridization occurring between the rare bird and the great crested tern.
The Chinese crested tern — a white, migratory bird with the black tip to the yellow beak — was first spotted in 1861 but has always been rare. It is listed as “critically endangered” on the International Union for Conservation of Nature’s Red List, with fewer than 100 individuals globally.
Chen said that at all of the bird’s breeding sites on the Chinese mainland and Taiwan, Chinese crested tern nests were found within great crested tern colonies.
He said the two species were members of the same Sternini tribe, but they diverged about a million years ago.
The hybrids are difficult to identify, Chen said. Only molecular genetic analysis can provide reliable identification and determine the extent of interbreeding between the species. But if the hybridization continues, the Chinese crested tern will eventually lose its natural appearance, as its white feathers evolve into gray ones like those of the great crested tern.
Since 2013, Chen’s team has been using artificial means to attract wild Chinese crested terns to breed on conservation islands in Ningbo, Zhejiang, to increase the success rate of pure breeding. By the end of last year, 51 of the rare birds had been born at the sites.
The team’s research paper was published in the latest issue of the international ornithological journal IBIS.