Family: Ciconiidae
Genus/Species: Leptoptilos crumeniferus
Description
To the casual observer the massive Marabou Stork with its balding, scabby head and pendulous pink air sac may appear to be one of the ugliest creatures in the world. If this same observer were to notice the Marabou's fondness for carrion and its habit of squirting excrement onto its own legs he or she would probably consider the original opinion to be justified. It takes a real bird lover to see past all of this stork's bizarre adornments to recognize the scruffy charm underneath.
The most distinctive feature of the Marabou is the nearly bald, spotted, scab-encrusted head, with its huge meat-cleaver bill. Dark, wispy hair-like feathers are scattered sparsely across the head, neck, and nape. The bare skin of the head and neck is predominantly pink to magenta in color, with spots of darker pigmentation concentrating around the face and extending down into the upper portion of the horn-colored bill. In breeding season the back of the neck turns a beautiful pale blue-green, and the spots on the face and forehead become encrusted with dried blood.
Two large inflatable subcutaneous air sacs complete the catalog of the Marabou’s peculiar features. One bright pink medium-sized bulbous sac protrudes from the feathers of the upper back. A larger pendulous flesh-colored gular sac hangs below the throat when inflated. The deflated gular sac can be concealed behind an incongruously attractive ruff of white neck feathers.
The Marabou’s back and wings are dark slate-gray with a touch of green iridescence on the wings and pale blue iridescence on the back. The feathers of the neck ruff, chest and belly are white. The scientific name Leptoptilos, Lepto = fine and ptilo = feather, refers to the long, pure-white, elegant, fluffy undertail-coverts that were once in great demand by the millinery trade.
Their eyes are grayish-brown. The skin of the legs and feet is naturally dark gray to black but appears to be much lighter due to the encrustation of excrement.
Juvenile storks are darker in plumage than the breeding adults. They have more extensive feathering about the head and neck. Their bare parts are less brightly pigmented. Bills are generally shorter and may take up to two years to reach their full adult length.
Distribution and Habitat
The Marabou Stork is found throughout most of tropical Africa. They prefer dry open savannahs near large lakes or rivers. They will often leave an area when the rainy season arrives and not return until the conditions are arid once again. Their wanderings are designed to keep them in close proximity to the largest concentrations of prey. Marabous are often found around fishing villages, slaughterhouses, and rubbish dumps.
Diet
Marabou Storks will eat just about any kind of animal, dead or alive. Living prey includes termites, fish, locusts, grasshoppers, army-worm caterpillars, frogs, rodents, crocodile eggs and hatchlings, quelea nestlings, doves, young and adult flamingos, cormorant nestlings, and pelican chicks.
Marabous evolved their naked heads and necks as an adaptation for feeding on large animal carcasses without getting their head feathers soiled with blood and gore. More than 200 Marabous were seen feeding on a single elephant carcass in Kruger National Park. They rely on vultures and other scavengers to open the tough outer hides and then use their cleaver-like bills to retrieve and then swallow surprisingly large pieces of meat. They are not above stealing morsels from other smaller scavengers.
Though there are fewer natural carcasses available from large predators these days, Marabous have readily adjusted their behavior to take advantage of the man-made carrion constantly available at garbage dumps, fishing camps, and abattoirs. Marabous can become rather tame and will stand with a few feet of workers cleaning carcasses, patiently waiting for scraps. A Marabou in Kenya swallowed an entire bloody butcher knife that had been set down momentarily by an abattoir worker. The spotlessly clean knife was found a few days later where the stork had apparently regurgitated it in the same manner it would indigestible natural foods.
Reproduction
Marabou Storks nest in colonies, often in association with other species of Ciconiiformes and waterbirds such as Abdim’s Storks, Yellow-billed Storks, Pink-backed Pelicans, herons, egrets, ibises and cormorants. Most colonies consist of 20-60 pairs but may number in the thousands. Individuals will return to the same colony and nest site year after year. Prime colony locations are relatively free of disturbance, near marshy habitat, and reasonably close to good food sources.
Male storks arrive at the nesting site first and establish themselves on a territory. They fully inflate their gular sacs and greet all arrivals with equal hostility. A courting female will respond to this aggression with passivity and a submissive display until she is accepted as a mate. Thereafter she will inflate her own gular sac and repel subsequent intruders.
Nests are placed in trees or occasionally on cliff-ledges. Though nest locations can be reused every year, the nest itself usually requires extensive renovations. The completed nesting platform is a structure of coarse sticks 1 m in diameter and 30 cm thick, lined with twigs and leaves.
The female lays 2-3 chalky white eggs. Both parents incubate for 29-31 days. The pale gray down of the newly hatched chicks is quickly replaced by a thicker covering of white down. Chicks grow rapidly in the first few weeks of life as their parents keep them constantly supplied with food regurgitated onto the floor of the nest. Their growth rate slows down as they begin to channel more of their energy into feather development. The pre-fledging period, 95-115 days, is relatively long in this species. Most birds reach sexual maturity in their fourth year and may live for more than 25 years.
Conservation
The willingness of the Marabou Stork to adjust to human activity has benefited the species. Populations may actually be increasing in some areas. Its grotesque appearance and unsavory habits have made the Marabou Stork an unattractive target for hungry hunters. The Marabou’s more enlightened neighbors appreciate its efficiency in reducing disease by cleaning up carcasses and other rubbish.
References:
Elliott, A. Family Ciconiidae (Storks) Pp. 436-455 in: Del Hoyo, J., Elliott, A. and J. Sargatal. eds. 1992. Handbook of the Birds of the World. Vol. 1. Ostrich to Ducks. Lynx Edicions, Barcelona.
Hancock, J.A., Kushlan, J.A. and M.P. Kahl. 1992. Storks, Ibises and Spoonbills of the World. Academic Press Limited, London.
Photo by Kate Volz, NZP
No comments:
Post a Comment