Identification Characteristics
Summer:
- The tips of the tertial feathers, sometimes including some of the longest, are dark gray with black feather shafts.
- The body of all wing feathers except the first is black.
- The remaining parts of the plumage are white.
- The under-neck feathers are long, and the tertial feathers are longer than the primary feathers.
Winter:
- The tertial feathers are no longer than the primary feathers.
- Eyes are reddish-brown.
- The beak is black.
- Bare skin on the neck and head is black with a slight bluish tinge.
- Bare skin on the flanks and underwings is dark red, and the legs are black.
Biology and Ecology
Diet:
- Includes frogs, snails, insects, and their larvae, and occasionally fish.
- Forages along the coast, in small or medium-sized flocks.
- Probes in mud or slow-flowing water to catch prey.
- Breeding season is only in June, July, and August.
- Nest construction takes 13-20 days.
- Lays 3-5 eggs; incubation period is 25-28 days.
- Prefers to live in wetlands, along riverbanks, and in ponds, and can also be found in flooded grasslands.
- Exhibits colonial nesting behavior.
Distribution
In Vietnam:
- Primarily concentrated in the Mekong Delta, forming colonial nests in large bird sanctuaries in Bac Lieu, Ca Mau, and Tra Vinh provinces.
- Recently, a few individuals have been observed in the Red River Estuary and the Van Uc River Estuary (Hai Phong).
Worldwide:
- Pakistan, Nepal, India, Sri Lanka, Myanmar, Thailand, China, Japan, Laos, and Cambodia.
Value
- A rare gene source, one of the key bird species that constitute the bird sanctuaries in the Mekong Delta, especially in Bac Lieu, Ca Mau, and Tra Vinh provinces.
Status
- The population is declining due to multiple factors, including habitat loss of foraging grounds in wetlands, and food contamination with chemicals used in agriculture.
- The taking of chicks and eggs at bird sanctuaries greatly affects the population growth of this species.
Classification
- VU A1c,e B1+ 2b. (Vulnerable)
Conservation Measures
- Protect bird sanctuaries in the Mekong Delta and foraging grounds in the Red River Estuary.
- Strictly prohibit any activities related to the exploitation of eggs and chicks in bird sanctuaries.
- Minimize the impact of fishing activities in coastal estuaries during the breeding season (April – September).