Identification:

• Size: 43–53 cm; wingspan 100–130 cm.
• Body: Grey upper parts and white under parts. It has a distinctive white forehead, glossy black cap with a long crest, crest recedes in the non-breeding season
• Beak:  Yellow
• Juvenile: Juveniles appear like non-breeding adults, with crown feathers brownish with pale spots, underparts and upper wings are barred and ashy brown.

Thalasseus bergii cristatus:

Northern-most breeding range in Ryukyu Islands and southeastern China up to the Yangtze Estuary, all-year-round to the Philippines, Southeast Asia, the Sunda Islands, Wallacea, New Guinea, Australia, and the tropical Pacific Ocean (to southeastern Polynesia).

Non-breeding movement is understudied. Satellite tracking showed those breeding in SE China winter in coastal Indo-China, Thailand, Myanmar and northern Philippines. Birds breeding at Paracel (Xisha) Islands in the South China Sea winter in central Philippines and Borneo. Non-breeding birds in Wallacea were mostly tracked to visit northern Australia where they may breed, with one tracked to Palau.

• Breeding habitat

Nests on offshore islands, low-lying sandy, rocky or coral islets, usually unsheltered bare surface. The bird forages in shallow waters in estuaries, lagoons and barrier reefs, along beaches, and also in the open sea. They may take rest on buoys or sandbars.

Breeding habitat of Greater Crested Tern in Zhejiang, China © Simba Chan

Dense nesting colony of Greater Crested Tern in Zhejiang, China © Simba Chan

• Non-breeding habitat

Greater Crested Tern wanders and disperses after the breeding season. They use sandy islands, coastal sandy or tidal flats.

Greater Crested Tern resting on buoy ©Kenneth Lam

Global estimated population: The global population is estimated to number c.150,000-1,100,000. while regional population estimates in EAA Flyway are 100,000-1,000,000 according to the 1^st Conservation Status Review.

However, the estimation seemed to lump several populations together. From present knowledge the Greater Crested Tern breeding along the coasts of Zhejiang, Fujian, Taiwan and Guangdong are likely belonged to one population that migrates to Indo-china, Thailand, Myanmar and the northern Philippines. This population is probably around 30,000 birds with an increasing trend.

• Human disturbance, e.g. recreational and tourism activities in coastal areas close to breeding colonies
• Egg collection
• Habitat loss

(Note: A regular migratory stop-over site for this species and many other terns and shorebirds, the tidal flat of Pamawaran, Bulacan in Manila Bay, the Philippines, is currently under threats from reclamation for airport expansion. Hundreds of Greater Crested Terns, including up to 10 individuals color-banded from Zhejiang and Taiwan, have been recorded at these sites since 2021.)

GCT color-banded in Zhejiang, China sighed at Manila Bay, the Philippines on 28 October 2022 © Irene Dy

Other threats:

• Pollution
• Plastic pollution
• Over-fishing

Natural threats:

• Adverse weather conditions, e.g. typhoons, heavy rains, strong winds and waves
• Natural predators (e.g. gulls, Peregrine Falcon, snakes, rats)

Satellite tracking study of Greater Crested Terns in collaboration with Indonesia shed light to conservation of Criticallty Endangered Chinese Crested Tern wintering ground

Greater Crested Terns provide socia protection to the critically endangered Chinese Crested Terns in both breeding and wintering grounds. Studying both or either one species could provide useful information for the conservation of both crested terns. HKBWS in collaboration with partners in Indonesia conducts satellite-tracking studies of the Greater Crested Terns in Wallacea region of Indonesia since 2018. Previously we assumed the Greater Crested Terns in this area could have a northern breeding origin, through the tracking study we could find out migration routes and stopover sites of Greater Crested Tern and potentially to the Chinese Crested Terns too.

The results brought us unexpected findings that birds in Wallacea region migrated south to the Gulf of Carpenteria of northern Australia for breeding and one bird migrated to Palau. These birds stayed in the areas where are the known tern breeding sites. Non-adults did not migrate to these breeding areas but wandered around Banda Sea, Timor Sea and Arafura Sea. Migration route and hotspots are now being identified with this study as site and habitat management could now be considered to apply in the important sites. This finding can also help promoting seabird conservation collaboration between Indonesia, Australia and other neighouring countries.

Mr. Yu Yat Tung, Research Manager of HKBWS released a Greater Crested Tern fitted with a satellite transmitter in the wintering island of Indonesia © HKBWS

Greater Crested Tern fitted with satellite transmitter in Indonesia © Simba Chan

Learn more: https://www.hkbws.org.hk/cms/en/hkbws/cct2019

Tubbataha Reefs Natural Park  holds the largest breeding colony of Greater Crested Terns in the Philippines with at least 14,000 individuals as of the last survey.  They breed in the two islets of Tubbataha.  These breeding grounds are off limits to tourists to prevent stress and disturbance especially during the breeding months of March to July. Marine park rangers conduct monthly estimates of adults and a more comprehensive quarterly inventory which includes eggs, pulli, and juveniles.

The Philippine Red List of Threatened Fauna classifies the  Greater Crested Terns as Vulnerable.

Tubbataha Reefs Natural Park ©Godfrey Jacosalem

Tubbataha Reefs Natural Park ©Kymry Delijero

Although Greater Crested Tern is among one of the biggest terns, it is a very nerous breeder. They tend to form very big and dense nesting colonies thus easy to be found during breeding season. Because the critically endangered Chinese Crested Terns nest in the same colony amid Greater Crested Terns in Zhejiang, Fujian and Taiwan, attracting Greater Crested Tern to breed in desired protected site supported restoring the population of Chinese Crester Tern. Hybridization is reported but the threat is much lower than commonly believed as they have a very strong sense of species identify. Hybrid birds (which may be the result of wrong imprinting) are very difficult to find a mate (pers. obs.).

Chinese Crested Tern is a close relative to Greater Crested Tern, so close that the type specimen of Chinese Crested Tern collected near Halmahera, Indinesia in 1861 was long regarded as a Greater Crested Tern (corrected since 1975), and a specimen of Chinese Crested Tern collected near Chemulpo (now Incheon), Korea in 1917 was also misidentified as a Greater Crested Tern (corrected since 2016).