Satellite Trackers Reveal Transborder Migration Routes of Endangered Bird

A team led by Prof. Hsiao-Wei Yuan (袁孝維) of the School of Forestry and Resource Conservation has completed a 10-year research project that has provided much needed insight into the mating habitats and international migration routes of the endangered Chinese crested tern (Thalasseus bernsteini) and its more common cousin, the greater crested tern (Thalasseus bergii). Prof. Yuan began the project in 2008, when the Forestry Bureau and Lienchiang County Government commissioned her together with the Wild Bird Society of Taipei to initiate research that would help better protect the rare tern.

The Matsu and Penghu archipelagoes are important breeding grounds for the Chinese crested tern, which came to be called the "bird of myth" because it had not been observed for many years and was feared to be possibly extinct. Although ornithologists and birdwatchers breathed a sigh of relief back in 2000 when film director Chieh-Te Liang (梁皆得) observed a small group in the Matsu Islands Tern Refuge, the bird remains a critically endangered species and the rarest of the Laridae family of birds.

Prof. Yuan's research team employed satellite tracking devices to trace the transborder migration routes and the stopover sites between the birds’ mating grounds on the island chains of Matsu and Penghu and their wintering grounds overseas. However, in order to avoid any possible harm to the struggling species, the team opted to attach its tracking devices to greater crested terns, which are categorized as a species of least concern in terms of survival. Since the Chinese crested tern and greater crested tern migrate together and share common breeding grounds, Prof. Yuan and her researchers were able to infer the international flyways of the Chinese crested tern from the tracking data they obtained from their greater crested tern subjects.

From 2008 to 2017, the researchers released a total of 24 greater crested terns carrying satellite trackers, a combined 20 from Matsu in 2008, 2016, and 2017 and an additional four from Penghu in 2015 and 2016. The birds' tracking signals revealed that the greater crested terns of Matsu and Penghu branch into two southbound flyways as they leave Taiwan in August and September. One route crosses the Taiwan Strait to wintering grounds in the Philippines, while the other follows the southeast coast of China en route to winter destinations in Vietnam, Thailand, and Cambodia, and even as far as Myanmar.

Data from the 2016 Matsu release showed that greater crested terns are also active in marine areas near the islands of Taiwan's Kinmen County off the coast of China. Moreover, other data revealed a difference in the makeups of the greater crested tern populations of Matsu and Penghu, with 75% of the greater crested terns of Matsu coming from mainland Southeast Asia and 75% of the Penghu terns originating in the Philippines.