Wattled Crane

About the wattled crane

The wattled crane is a large, threatened crane found in the wetlands and grasslands of eastern and southern Africa, ranging from Ethiopia to South Africa. It was first formally described in 1789 by the German naturalist Johann Friedrich Gmelin, based on an earlier description and illustration by the English ornithologist John Latham. The species' scientific name comes from the Latin caruncula, "a small piece of flesh," a reference to its wattles. The species has long been shuffled between genera: it was traditionally placed in its own genus, Bugeranus, then moved to Grus after a 2010 molecular study found it to be a sister species to a group containing the blue crane and demoiselle crane, though some taxonomists still classify it under Bugeranus. It has no recognized subspecies.

Standing 150 to 175 cm (4 ft 11 in to 5 ft 9 in) tall, the wattled crane is the largest crane in Africa and the second-tallest crane species in the world, behind only the sarus crane; among all birds native to Africa, only the two ostrich species stand taller. Its wingspan runs 230 to 260 cm (7 ft 7 in to 8 ft 6 in), body length is 110 to 140 cm (3 ft 7 in to 4 ft 7 in), and it weighs 6.4 to 8.28 kg (14.1–18.3 lb) in females and 7.5 to 9 kg (17–20 lb) in males, making it the heaviest, on average, of Africa's large long-legged wading birds and roughly the fourth-heaviest flying bird on the continent. The back and wings are ashy gray, the crown and area above the eyes are dark slate gray, and the rest of the head is white, including the mostly feathered wattles that hang beneath the throat. The breast, flight feathers, and tail coverts are black, and the skin from the eye to the base of the bill and the tips of the wattles is bare, red, and covered in small wart-like bumps. The legs and toes are black, males and females look almost identical apart from slightly larger males, and juveniles have tawny plumage without the bare facial skin or prominent wattles of adults. Among standard measurements taken for the species, the wing chord runs 61.3–71.7 cm (24.1–28.2 in), the exposed culmen (the visible ridge of the upper bill) 12.4–18.5 cm (4.9–7.3 in), and the tarsus 23.2–34.2 cm (9.1–13.5 in); three adult wattled cranes measured in one sample averaged 8.15 kg (18.0 lb). The species has a generation length of 13 years.

Behavior and diet

Wattled cranes inhabit fairly inaccessible wetlands, favoring shallow, marsh-like habitat with plenty of sedge vegetation. Like all cranes, they are omnivorous, but the wattled crane leans more heavily on plant food than most: the bulk of its diet is the tubers and rhizomes of submerged sedges and water lilies, supplemented by aquatic insects and, opportunistically, snails, amphibians, and snakes. Roughly 90% of foraging happens in shallow water, typically by digging into muddy soil with the bill; the species eats grain and grass seed far less often than Africa's other crane species.

Seasonal movements appear to track local water conditions rather than temperature, and numbers at a site can swing from almost none to as many as 3,000 birds during local floods. Outside the breeding season the birds are somewhat gregarious, with flocks of ten or more and occasionally up to 89 individuals; they share habitat and diet with the lechwe antelope and the spur-winged goose. Breeding begins around April, with nests built as sloppy, crushed impressions of grass at a marsh's edge, sometimes reusing an old spur-winged goose nest. Clutches average just 1.6 eggs — reportedly the smallest average clutch of any crane — and even when two eggs are laid, usually only one chick survives to fledge. Incubation lasts roughly 33 to 36 days, the longest of any crane, and both parents share the duty. Chicks start foraging with their parents at around 80 days and fledge at 100 to 150 days, again the longest fledging period of any crane; young typically stay with their parents for close to a year, until the next breeding season begins.

Range and habitat

The wattled crane occurs across eleven countries in eastern and southern Africa, including an isolated population in the Ethiopian Highlands. More than half of the world's wattled cranes live in Zambia, while the single largest concentration is found in Botswana's Okavango Delta. The species was first recorded in Uganda in 2011, in the Kibimba Rice region, and a newly discovered population turned up in Angola in April 2018.

Conservation status

The wattled crane is listed as Vulnerable on the IUCN Red List, in a 2018 BirdLife International assessment, and is covered by the Agreement on the Conservation of African-Eurasian Migratory Waterbirds. Habitat loss is the central threat: the destruction, alteration, and degradation of wetlands make the wattled crane perhaps the most habitat-sensitive of all cranes. Hydroelectric power projects and other water development have altered many of its floodplain habitats, and the species also faces pressure from human and livestock disturbance, collisions with power lines, aerial spraying for tsetse flies, and illegal collection of eggs, chicks, and adults for food.