Identification:
- Adult:
- Summer: Head and neck bare, occasionally with a few brown feathers. Back, wings, and tail are black with a greenish sheen, featuring a broad bronze patch near the tips of the largest secondary coverts. The longest scapular feathers and tertiary feathers are edged with white. Underwing coverts are black, belly is white.
- Winter: Lacks the bronze patch on the wings. Eyes are white. Bill is dull yellow, the tip is pale white during breeding season, and the base of the bill is red. Face and neck are bright yellow, with a reddish-brick hue during the breeding season. Bare skin on the crown is pale brown. Legs are pale green or pale black.
- Juvenile: Head and neck have many feathers; lacks the greenish sheen on the black feathers.
Biology – Ecology:
- Habitat: Mangrove forests, coastal mudflats, flooded grasslands, lakes, and rice fields.
- Diet: Primarily fish, occasionally consuming frogs and snakes.
- Breeding Season: From November to the following year. Often nests in tall trees near water, forming colonies. Lays two clutches, with an average of four eggs per clutch.
Distribution:
- Within Vietnam: South Central Coast and South Vietnam, commonly found in Dong Nai in mangrove forests (Cat Tien National Park), wetlands in the Plain of Reeds (Tram Chim, Tam Nong, Dong Thap), along the Mekong Delta coast and U Minh melaleuca forests, as well as Yok Don National Park (Dak Lak).
- Global: India, Sri Lanka, Myanmar, Southeast China, Thailand, Laos, Cambodia, Malaysia.
Value:
- Rare genetic resource with high scientific value.
Status:
- Population is severely declining, primarily due to habitat loss and disturbance from human economic activities such as agricultural expansion, particularly from the forest fires in the Mekong Delta.
IUCN Red List Category:
- VU A1c,e B 2a + 3b C 2 a.
Conservation Measures:
- Planning and rational use of wetlands as foraging grounds in the Mekong Delta, such as Tram Chim (Tam Nong-Dong Thap), and especially U Minh Thuong Melaleuca forest (Kien Giang), which is a nesting site.
Vietnam Red Data Book:
- Listed in Vietnam’s Red Data Book (1992, 2000) as Rare (R).