Screamers

The screamers are South American birds that are classed among the waterfowl but are very un-ducklike in appearance. There are three species: the horned screamer (Anhima cornuta), the northern or black-necked screamer (Chauna chavaria) and the southern or crested screamer (Chauna torquata – see photo). Of these, the southern screamer is widely distributed in the pampas regions of southern Brazil, Argentina, Paraguay and Uruguay, but the northern screamer, restricted to northern Colombia and Venezuela, is recognised as a threatened species. The horned screamer is found throughout northern tropical South America and is fairly common.

Appearance

Screamers are about the size of small turkeys, with the largest being the horned screamer which can reach 38 inches in length. Southern screamers are about 35 inches long and northern screamers are the smallest at around 30 inches.

The screamer’s head is rather small and slender, the bill short and curved, and the neck quite short. The wings are strong and armed with two sharp spurs on the forward edge of each. The legs are fleshy, with partial webbing between the front toes.

The three species show some variations in plumage, being generally dark grey to black with some white markings. The horned screamer is notable for the long spike that projects forward from the crown, whereas the other species have crests on the back of the head. The northern screamer is easily recognisable from the short downy black feathers on the neck that are framed by white rings above and below.

Anatomy

Screamers boast several unusual anatomical features. For one thing, their feathers grow continuously over their bodies with no bare spaces. This is something that only ostriches, penguins and colies (mousebirds) share. They are also the only birds that do not have “uncinate processes” on their ribs. These are bony projections that offer strengthening to the ribcage, and their lack has only ever been noticed elsewhere in the fossilised remain of Archaeopteryx, the proto-bird from the upper Jurassic period of 130 million years ago.

Another unusual feature is that almost all their bones are hollow, even the outer digits of the wings and toes, and they have a complex system of air sacs under the skin. This makes screamers very lightweight birds for their size, as well as helping their buoyancy on water.

Habitat and behaviour

Screamers inhabit marshes, wet grasslands and forest lagoons, where they can be seen walking on floating masses of vegetation. They find it difficult to take off from the ground or water, but once airborne they are strong fliers that can soar for hours and fly to great heights.

As the name suggests, screamers are very vocal birds with loud, gooselike calls that announce impending danger to all the wildlife in their area. Their powerful and far-carrying trumpeting can be heard day and night, either between breeding pairs or when assembled in flocks.

Screamers feed on vegetation, mainly the leaves and seeds of water plants. They are regarded as a pest in some areas where they feed on farm crops.

Breeding

During the breeding season screamers will fight each other for mates or to defend their territory, using the spurs on their wings as weapons. Should these break off they will eventually grow back.

A shallow nest of reeds and rushes is built on the ground and anything from two to six eggs are laid. Both partners incubate the eggs in turn, and this can take up to 44 days before the chicks hatch. The nestlings leave the nest and follow their parents very soon after hatching.

© John Welford