Adult Male Plumage:
Breeding Plumage: Features a metallic green band with white edges extending from the eye to the nape and onto the neck. The remaining head and neck are a dark brownish-black, with a slightly lighter chin and area in front of the eyes. The lower neck, back, shoulders, and flanks are white with black streaking, while the breast has larger streaks and black spots in the center. The lower back is brown with streaked feather edges. The flanks are brown, with each feather edged in a paler color. The belly is white.
The under-tail coverts are black, with reddish-brown sides. The wing coverts are pale greyish-brown, with the greater coverts edged in white. The speculum (wing patch) is metallic green with a bronze sheen, edged anteriorly with pale rufous and posteriorly by two black and white lines. The tertials (innermost flight feathers) are silvery-brown.
Winter Plumage: Resembles the female plumage, but the speculum exhibits a more vibrant blue sheen.
Female Plumage:
The head is brownish-black. The upperparts are dark brown, with all feathers edged in pale rufous. The area in front of the eyes, flanks, and neck are white, tinged with rusty-rufous, and have brown feather centers. The flanks and breast are white, tinged with rufous or rufous-brown, and have dark brown spots.
Eyes are brown. The male’s bill is black, while the female’s bill is yellowish or yellowish-green. Legs are greyish-yellow, sometimes with a hint of green.
Measurements:
- Wing Length:
- Male: 173 – 193 mm
- Female: 165 – 180 mm
- Tail Length: 70 – 97 mm
- Tarsus Length: 28 – 32 mm
- Bill Length: 35 – 41 mm
- Weight: 0.20 – 0.45 kg
Distribution:
This species is widely distributed across Europe and Northern Asia. In winter, it migrates southward throughout the coastal regions of Europe, from Norway to the Black Sea, West Africa, the Nile River basin, the Red Sea, Iraq, Iran, India, Myanmar, Thailand, northern Indochina, southern China, Korea, Japan, and the Philippines.
In Vietnam, it is found throughout the Red River Delta, particularly in estuaries, and along the coastal plains of central Vietnam, as far south as Thua Thien. It is also occasionally seen in inland water bodies in the midlands and mountainous regions.