The Sungrebe is a small, slim aquatic bird that swims while riding low in the water. The plumage is mostly brown, with a black crown and nape and conspicuous white stripes along the sides of its neck, as well as a white throat and chin. Females have a rufous patch on the side of the face. The long tail extends well beyond the body in flight. The Sungrebe also has lobed toes that are banded with dull yellow and black.
The Sungrebe is almost unmistakable: the small size and black and white stripes on the neck should distinguish it from all other aquatic species, such as ducks or grebes. In flight, note the long, broad tail.
The following description is based on Wetmore (1965), except where otherwise indicated:
Adult male: The crown, hindneck, and upper sides of the head are black, except for a conspicuous white postocular stripe extending from above the eye back to the upper neck. Below the eye, the side of the head is white or buff. The back and wing coverts are olive-brown; the remiges are fuscous; and the rump and uppertail coverts are brown. Rectrices black, narrowly tipped with white. The under tail coverts are grayish brown; the under wing coverts are dark gray; and the tail is black and tipped narrowly with white. The throat and foreneck are white with a black band at each side, which is sometimes united across the front. This band is separated from the black of the hindneck by a broad white line. There is a faint buffy brown band across the upper breast and adjacent sides, while the rest of the breast and the abdomen are white.
Adult female: Similar to the male. During the breeding season, the female has a cinnamon patch on the cheeks and the side of neck (Alvarez del Toro 1971).
Juvenile: Similar to adult, but with the cheeks and sides the neck white.
Iris: dark brown (Wetmore 1965). Bare edges of the eyelid are dull red, forming a narrow ring (Wetmore 1965). The eye ring becomes brighter in color in the female during the breeding season (Alvarez del Toro 1971).
Bill: In male, maxilla mainly black, mandible pale horn and grayish (Blake 1977). In female, maxilla and the base of mandible dull red; rest of mandible pale horn with a light gray tip (Wetmore 1965). The bill of the female turns scarlet during the breeding season (Alvarez del Toro 1971).
The upper tarsus is a dull brownish yellow. Lower tarsus is honey yellow with a band of dull black on the inner side. The toes and toe webbings are also honey yellow with black bands (Wetmore 1965).
Linear measurements are from Wetmore (1965) and based on specimens from Mexico, Costa Rica, Nicaragua, and Panama.
Total length: 28.0-30.5 cm
Males (n=6): wing, mean 141.3 mm (range 138.4-152.0 mm); tail, mean 86.7 mm (range 83.0-91.0 mm); culmen (from base), mean 31.5 mm (range 30.0-33.6 mm); tarsus, mean 23.5 mm (range 22.4-24.0 mm)
Females (n=6): wing, mean 137.7 mm (range 133.3-142.2 mm); tail, mean 80.1 mm (range 78.0-81.5 mm); culmen (from base), mean 30.3 mm (range 28.5-33.2 mm); tarsus, mean 22.7 mm (range 21.7-23.7 mm)
Mass: males 110-140 g, females 130-140 g (Haverschmidt 1968)