The South American Bittern (Botaurus pinnatus), widely known as the Pinnated Bittern, is a large member of the heron family found in the New World tropics. Like the other Botaurus bitterns, its plumage is mostly buffy-brown and cryptically patterned. Though it is a widespread species, it is rarely seen"?presumably due to its skulking habits"?and much about its life history remains little known.

Description

The South American Bittern is a large heron, measuring between 63.5 and 76 cm (25"?30 in) with a weight of roughly 800 grams (1.8 lb). Sexes are similarly plumaged, but females tend to be smaller than males.

Both adults and immatures are generally buffy, though heavily marked with cryptic patterning. Juveniles tend to have a somewhat more reddish ground color. The throat is unmarked white, the foreneck is white broadly streaked with pale brown, and the rest of the neck is buff with thin black barring. The breast and belly are white with broad pale brown streaks, while the back is buff, heavily streaked and barred with black. Rectrices are black in males and brown in females.

The bill is stout and strong, yellowish overall with a dusky upper mandible. The bare facial skin is bright yellow, with a brown line running across the lores. The legs are greenish-yellow, and the iris is yellow.

Slate gray remiges create a conspicuous two-toned effect in flight.

Taxonomy

German naturalist Johann Georg Wagler, who first described the South American Bittern in 1829, placed it in the genus Ardea. It is sometimes included in a superspecies with American Bittern, and these two species are sometimes further included in a superspecies with Eurasian Bittern. There are currently two recognized subspecies, which are separated by a gap in Central America.

• B. p. caribaeus is found in eastern Mexico, Belize and (rarely) Guatemala. It has a longer bill, and shorter wings and tail than the nominate race, as well as less streaking on the throat.
• B. p. pinnatus is found from southeastern Nicaragua to Ecuador and the Guianas, south through Brazil to Paraguay and northeastern Argentina.

Distribution and habitat

The name South American Bittern is a bit misleading, as the species is found as far north as southern Mexico. Its range stretches from the Atlantic slope of southeastern Mexico to northern Argentina, though there are few records for Guatemala and none for Honduras. It can be found in a variety of freshwater habitats, including dense Phragmites reedbeds, lakes with borders of cattails (Typha), rushes, tall sedges or water hyacinth, flooded tall-grass pastures, marshes and overgrown ditches.

Estimates of its population, and of overall population trends, are unknown.

Behavior

The South American Bittern is largely nocturnal. Though generally solitary, it will gather in small loose groups at favored feeding areas. When frightened, it tends to freeze with its body crouched low and its head raised vertically just high enough to see. It typically flushes only at close range.

Food and feeding

Its diet is varied, consisting of fish, reptiles, amphibians, insects and small mammals, all of which are typically taken in ambush. The South American Bittern is a patient hunter, often standing motionless for long periods while waiting for prey to move within range.

Breeding

Unlike many herons (but like other bitterns), the South American Bittern is a solitary breeder. Its nest, a platform or shallow cup of rush stems or other plant material, is typically built among thick vegetation not far above the water surface. The female lays two to three olive-brown eggs, and is thought to do all of the incubation. South American Bitterns are almost exclusively wet season breeders.

Voice

If flushed, the South American Bittern gives a rough rawk-rawk-rawk call. During the breeding season, the male booms at dusk and into the night; his call is a deep poonk or poonkoo.