Appearance

A cryptic bird, except when displaying. The Sunbittern has a very long, thin neck with a long tail and long, pointed bill. Head is dark with two white stripes, above and below the eye. Remainder of plumage is barred in black, brown, and white, except for the stunning chestnut, black, and gold patterns visible when the wings and tail are spread.

Very distinctive. Possibly could be mistaken for a small heron, but Sunbitterns have much shorter legs and longer tails. The body in general also seems longer and more horizontally-oriented than a heron.

Adults: Neck long and extremely thin, tail and back end of body also fairly long. Head is black with a white superciliary and a white malar stripe. Throat white, the white extending down the front of the neck and the center of the breast and belly, becoming variably buffier and mottled with black and brown, but still lighter than the rest of the body. Undertail coverts are white to light buff with some fine barring. Back and sides of neck are finely barred in black and rufous, becoming denser down the back and lighter along the flanks. Mantle is buffier in male and more slaty or black in female.

Scapulars are grayish-brown to black with large white spots. Wings and tail are barred with black and gray. Extended wings show a sun pattern of buffy gold on all but the tips of the primaries, extending onto some of the secondaries and greater coverts. A band of chestnut and black covers the bases of the inner primaries and is also present towards the tips of the outer primaries. The fanned tail also shows two bands of black and chestnut.

Juveniles: Similar to that of the adult (Ridgway and Friedmann 1941, Thomas and Strahl 1990).

Chicks: see Reproduction.

Little information, other than some notes from Haffer (1968) on populations in northern South America. In this region, molt occurs during the second half of the year, between July and January. A pause occurs from February to May when the birds are breeding.

Primaries: Molted in descending order (with the innermost primary represented by P1), usually one at a time but with some specimens showing two growing feathers at a time.

Secondaries: Molt begins simultaneously at S1, S5, and S10 (with the outermost secondary represented by S1), the proceeds inward, though irregularities seem common.

Tail: Molt begins with the central feathers and proceeds outward, with some irregularities documented.

Data from Deignan (1936), Wetmore (1965):

Irides: red; eyelids yellow.

Bill: very long and pointed. Maxilla mostly black, but brownish basally and with tip orange-yellow. Mandible bright orange.

Tarsi and toes: bright orange, front of tarsus and upper surface of toes brown-orange.

Except where indicated, linear measurements are from Blake (1977):

Eurypyga helias major

Wing (chord): male mean 223 mm (range 216-230 mm, n=7), female mean 222 mm (range 218-229 mm, n=8)

Tail: male mean 151 mm (range 148-156 mm, n=7), female mean 150 mm (range 147-155 mm, n=8)

Culmen (from base): male mean 62.8 mm (range 61.1-65.1 mm, n=7), female mean 63.4 mm (range 61.1-67.3 mm, n=8)

Tarsus: male mean 55.4 mm (range 54.1-58.0 mm, n=7), female  mean 57.1 mm (range 54.6-59.3 mm, n=8) (Wetmore 1965, based on specimens from Panama and Colombia)

Eurypyga helias helias

Wing (chord): male mean 215.6 mm (range 204-231 mm, n=7), female mean 217.8 mm (range 208-227 mm, n=9)

Tail: male mean 158.5 mm (range 153-165 mm, n=7), female mean 158.8 mm (range 154-167 mm, n=9)

Culmen (from base): male mean 61.7 mm (range 59-65 mm, n=7), female mean 60.3 mm (range 57-65 mm, n=9)

Eurypyga helias meridionalis

Wing (chord): male mean 229.6 mm (range 226-237 mm, n=3), female mean 224.6 mm (range 220-229 mm, n=5)

Tail: male mean 160 mm (range 156-163 mm, n=3), female mean 153.4 mm (range 150-157 mm, n=5)

Culmen (from base): male 66 mm (range 61-72 mm, n=3), female mean 65 mm (range 61-69 mm, n=5)

Total length: 430-480 mm (Blake 1977)

Mass: male 199-295 g, female 188-211 g (Haverschmidt 1968)