Storks

(Ciconiidae)

Class Aves

Order Ciconiiformes

Suborder Ciconiae

Family Ciconiidae

Thumbnail description
Distinctive medium to large wading birds with long legs, long necks, and large powerful bills

Size
30–60 in (75–152 cm); 2.9–19.7 lb (1.3–8.9 kg)

Number of genera, species
6 genera; 19 species

Habitat
Wide variety of mainly lowland habitats, generally in warm climates. Many species prefer to be in or near wetlands, though some occur in drier areas

Conservation status
Endangered: 3 species; Vulnerable: 2 species; Near Threatened: 2 species

Distribution
Widely distributed; found on all continents except Antarctica.

Evolution and systematics

There are 19 species of stork in six genera. Taxonomists place the birds in three "tribes": the Mycteriini (including the wood stork (Mycteria americana) and the openbills (Anastomus spp), the Ciconiini (including the European white stork (Ciconia ciconia) and black stork (Ciconia nigra) and the Leptoptilini (including large storks such as the marabou (Leptoptilos crumeniferus) and jabiru (Jabiru mycteria).

Stork remains have been identified from the Upper Eocene (about 40 million years ago) in France, and the group was distinct in the early part of the Tertiary (about 65 million years ago). Traditionally storks are placed taxonomically with other long-legged wading birds such as herons, but their nearest relatives may be New World vultures such as the ubiquitous turkey vulture. Although the similarities are not immediately apparent, DNA analysis supports this conclusion. Interestingly, both New World vultures and storks share the rather unpleasant habit of defecating on their own legs to facilitate heat loss, and this has been cited as a behavioral similarity to support the biochemical findings.

Physical characteristics

Storks are distinctive medium to large wading birds. They have long legs, long necks, and large powerful bills. The only birds with which they might be confused are herons, but in general herons are of a much slighter build and characteristically fly with neck retracted, as opposed to storks who fly mostly with their necks outstretched. Plumages are combinations of white, black, and gray. Strikingly colored bills in various combinations of red, black, and yellow often complement these plumages. Some species, such as the North American wood stork and the African marabou, lack feathers on their head and neck, a response to their habit of feeding in muddy pools and on carcasses, situations in which feathers would soon become soiled.

Distribution

Storks have a wide distribution and are found on all continents except Antarctica. They reach their greatest diversity in tropical regions and show a strong preference for warmer climates; indeed the few species that breed in colder temperate areas migrate to warmer countries after nesting. North America has the least diversity, with the wood stork as the region's only, and very marginal, representative.

Habitat

Storks are found in a wide variety of mainly lowland habitats. Many species prefer to be in or near wetlands, although some, such as the marabou, occur in drier areas. The stork with possibly the most atypical habitat is the black stork. In the northern summer, this bird inhabits the extensive forests of Eastern Europe and Asia, albeit within easy reach of small pools and rivers for feeding.

Behavior

The social behavior of storks is varied. Many species, such as the painted stork, nest in colonies and are highly gregarious

during the breeding season. Others nest in smaller, much looser, groups, and a few species, such as the black stork and saddlebill (Ephippiorhynchus senegalensis), nest alone. Outside breeding season, storks are either solitary or congregate in small groups.

Storks are adept at soaring in flight and regularly exploit warm currents of rising air (thermals) to gain height before gliding down to their destination. Most fly with necks outstretched, although those with particularly heavy bills, such as the marabou, may retract them to keep their aerial balance. Storks rarely fly in formation.

Although storks are not very vocal, they can produce a variety of croaks, honks, hisses, and wheezes. They are also well known for their noisy bill-clattering displays during the breeding season. In the towns and villages where the stork often breeds, the clattering can go on well into the night, to both the chagrin and delight of residents.

Feeding ecology and diet

Storks are carnivores and consume a wide variety of animals, from small aquatic invertebrates, amphibians, and fish to more unlikely items such as young crocodiles and young birds. Two closely related species, the marabou and the greater adjutant, are at home scavenging at carcasses and even on human waste.

Such a varied diet elicits a similarly varied range of feeding techniques. Some species, such as the wood stork, hunt almost entirely by touch, capturing small fish the moment they chance to touch the bird's sensitive bill, which is purposely held open in readiness. In experiments, wood storks have been recorded reacting in 25 milliseconds, the fastest-known response rate of any vertebrate.

The gap between the mandibles of the bill of the openbill has prompted much speculation as to its purpose in relation to the bird's feeding technique. Some observers have speculated that it might be used to break the shells of the openbill's preferred prey, apple snails (Pomacea); others have thought that the opening might help the birds carry the snails. Neither of these appears to be the case. It is perhaps more likely that the curvature of the lower mandible was originally a simple deformity that had the advantage of enabling some birds to extract snails from their shells more efficiently. Natural selection then favored these birds and the trait was perpetuated.

Other species, such as members of the Ciconiini tribe, are more opportunistic, and simply take what is available. Their typical feeding method involves slowly pacing their feeding grounds looking for prey which, when located, is seized with a sudden forward lunge.

Reproductive biology

Storks are either highly colonial, loosely colonial, or solitary breeders. Solitary breeders form monogamous pairs. Mycteria, Anastomus, and Leptoptilos are decidedly colonial, their chosen breeding sites sometimes consist of thousands of nests, often in the company of other storks, as well as wading birds such as herons and egrets. European white and maguari storks (Ciconia maguari) are much less colonial, breeding in smaller groups or, occasionally, alone. A number of storks, such as the black stork, woolly-necked stork (Ciconia episcopus), and jabiru always nest alone.

Almost invariably storks choose to nest in trees, and often at quite a height. Some species, such as the wood stork, prefer

the security of islands. Abdim's stork (Ciconia abdimii) will nest on cliffs or on the top of village huts, and the European white stork is renowned for nesting on structures such as telegraph poles, chimney stacks, and pylons.

Stork nests are made from sticks and twigs, with other plant materials occasionally woven into the final construction. As with some other wading birds, nest building is shared between male and female. Often the tasks are split, with the male collecting sticks and the female arranging them. The final nests, especially if built on older nests, can be huge. In the case of the European white stork, they have been known to be as much as 9 ft (2.7 m) in depth.

The eggs are oval and white, the average clutch size is five, and incubation lasts between 25 to 38 days, depending on species. After hatching, the young are completely dependent on their parents, who attentively bring and regurgitate food on the nest floor for the young to pick at. Chick development is rapid. Once the young have fledged they leave the nest, but may still remain dependent on their parents for support for some weeks. Most storks only reach breeding condition at between three and five years.

Conservation status

Birdlife International lists three species as Endangered (Oriental white stork, Storm's stork, and greater adjutant) and two as Vulnerable (lesser adjutant and milky stork). The painted stork and the black-necked stork are listed as Near Threatened. Many other species are suffering regional declines in the face of ever-increasing pressure for land for agriculture and building development. The wood stork suffered catastrophic declines in the southeastern United States following the wholesale drainage of wetlands such as the Everglades in Florida. However, the numbers of marabou are increasing, perhaps in part due to their fondness for feeding around human garbage.

Significance to humans

Storks are frequently held in great affection by local people across the world. In western countries the stork is often cited as the bird that brings babies. The roots of this myth are unclear, but it may be linked to the notion that storks nesting on houses will ensure fertility in the household. The welcome white storks receive is mirrored in other species, and many colonies are afforded special protection. In Thailand, Asian openbills (Anastomus oscitans) nesting in the grounds of a Buddhist temple at Wat Phai Lom have been protected by the monks for many years.

Species accounts

List of Species

Wood stork

Mycteria americana

subfamily

Tribe Mycteriini

taxonomy

Mycteria americana Linnaeus, 1758, Brazil ex Marcgraf. Monotypic.

other common names

English: Wood ibis; French: Tantale d'Amérique; German: Waldstorch; Spanish: Tántalo Americano.

physical characteristics

Length 33–40 in (83–102 cm), wingspan 59 in (150 cm). Weight 4.4–6.6 lb (2–3 kg). White with gray featherless neck and head; long, slightly downcurved bill.

distribution

Southeastern United States, through tropical Central and South America to northern Argentina.

habitat

Wetlands with shallow water.

behavior

Highly social, nests in colonies, and feeds and roosts in flocks.

feeding ecology and diet

Mostly fish, found almost entirely by sense of touch.

reproductive biology

Nests colonially in trees. Clutch size three eggs; incubation 28–32 days; fledging 60–65 days.

conservation status

Not threatened, but suffered historical declines in the United States.

significance to humans

Regarded as a "barometer" of wetland quality in the United States.

Painted stork

Mycteria leucocephala

subfamily

Tribe Mycteriini

taxonomy

Tantalus leucocephalus Pennant, 1769, Ceylon. Monotypic.

other common names

English: Painted wood stork, Indian wood ibis; French: Tan tale Indien; German: Buntstorch; Spanish: Tántalo Indio.

physical characteristics

Length 3–3.3 ft (93–102 cm), wingspan 4.9–5.2 ft (150–160 cm); 4.4–7.8 lb (2–3.5 kg). Black and white with orange/red face and yellow bill slightly downcurved at the tip.

distribution

India and Indochina.

habitat

Shallow freshwater lakes, marshes, and flooded fields.

behavior

Gregarious. Flies with neck extended and slightly lowered. Generally quiet, but performs "wing-woofing" and bill-clattering during courtship displays.

feeding ecology and diet

Mostly fish, but also frogs, small reptiles, and invertebrates. Locates prey by touch, stalking shallow water with an open bill, using feet and wing flaps to disturb prey.

reproductive biology

Colonial, up to 100 nests together. Clutch size three to four, incubation 28–32 days, fledging 60 days.

conservation status

Not threatened. Local declines have occurred though through hunting and capture for zoos.

significance to humans

Popular species whose colonies are actively supported and protected by locals.

Asian openbill

Anastomus oscitans

subfamily

Tribe Mycteriini

taxonomy

Ardea oscitans Boddaert, 1783, Pondicherry. Monotypic.

other common names

English: White openbill; French: Bec ouvert Indien; German: Silberklaffschnabel; Spanish: Picotenaza Asiático.

physical characteristics

Length 31 in (81 cm), wingspan 58–59 in (147–149 cm). Small pale gray or white stork with black wings and black forked tail. Distinctive "open" bill formed by lower mandible curving down, then back, to meet upper mandible at tip.

distribution

India, Indochina.

habitat

Shallow marshes and flooded fields.

behavior

Social. In flight soars on thermals, then glides to destination. Call a mournful "hoo-hoo."

feeding ecology and diet

Mainly apple snails and occasionally other small aquatic animals. Prey located by touch and sight. Snails extracted from shells using sharply pointed lower mandible.

reproductive biology

Highly social, nests in large tree colonies with other waterbirds such as herons. Clutch size two to five eggs, incubation 27–30 days, fledging 35–36 days.

conservation status

Not threatened. The most common Asian stork.

significance to humans

Generally well regarded. Specially protected in Thailand, where colonies are located in the grounds of Buddhist monasteries.

Black stork

Ciconia nigra

subfamily

Tribe Ciconiini

taxonomy

Ardea nigra Linnaeus, 1758, Sweden. Monotypic.

other common names

French: Cigogne noire; German: Schwarzstorch; Spanish: Cigüeña Negra.

physical characteristics

Length 37–39 in (95–100 cm), wingspan 57–61 in (144–155 cm); 6.6 lb (3 kg). Glossy black except for white feathering on belly. Red bill can appear slightly recurved.

distribution

Largest breeding range of any stork, nesting from eastern Europe through central Asia. Winters in Africa and Asian tropics. Separate resident population occurs in southern Africa.

habitat

Wooded areas with access to water.

behavior

More solitary than some other storks. Agile flier, can fly through the forest canopy. More vocal than other storks, communicates with variety of hisses and whistles.

feeding ecology and diet

Fish and occasionally aquatic invertebrates. Locates prey visually, grabbing food items with forward lunge of the head. Has been observed shading water with outstretched wings while hunting.

reproductive biology

Monogamous. Solitary nester in trees, the same nest often used over many seasons. Sometimes "adopts" other bird nests, such as those of black eagles and hammerheads. Clutch size three to four eggs, incubation 32–38 days, fledging 63–71 days.

conservation status

Declining locally from persecution and deforestation, especially in Europe.

significance to humans

Heavily hunted, especially during migration through southern Europe and Asia.

European white stork

Ciconia ciconia

subfamily

Tribe Ciconiini

taxonomy

Ardea ciconia Linnaeus, 1758, Sweden. Two subspecies.

other common names

English: White stork; French: Cigogne blanche; German: Weisstorch; Spanish: Cigüeña Blanca.

physical characteristics

Length 39–40 in (100–102 cm), wingspan 61–65 in (155–165cm); 5.1–9.7 lb (2.3–4.4 kg). Mostly white with black on wings and red/orange bill and legs.

distribution

Summer breeding population in Europe and western Asia, wintering in tropical Africa and India. A resident population also in South Africa.

habitat

Open spaces without tall and thick vegetation, frequently in or near wetlands. Will nest in towns and villages.

behavior

Less gregarious than other storks, but migrates in groups. Adept at soaring on thermals during long migrations along well-defined routes. Uses bill-clattering in displays.

feeding ecology and diet

Varied diet of animal matter, from insects and earthworms, to lizards, snakes, and amphibians. Locates prey by sight.

reproductive biology

In temperate north, nesting starts between February and April. Nests are large constructions of sticks lined with a variety of soft natural or human-made objects located in trees or on suitably tall human-made structures. Loosely colonial, but may nest alone. Clutch size averages four eggs, incubation 33–34 days, fledging 58–64 days.

conservation status

Significant local declines in Western Europe, where it is Threatened. Declines linked to the reduction of swarms of locusts (an important source of food) in west African wintering grounds, and reduction of food-rich habitats in breeding areas as a result of the intensification of agriculture. Also threatened by hunting and collisions with power lines.

significance to humans

Traditionally a popular bird, nesting on houses is welcomed as conferring good fortune and fertility to householders. Also some economic value as pest controllers.

Saddlebill

Ephippiorhynchus senegalensis

subfamily

Tribe Leptoptilini

taxonomy

Mycteria senegalensis Shaw, 1800, Senegal. Monotypic.

other common names

English: African jabiru, saddlebilled stork; French: Jabiru de Sénégal; German: Sattelstorch; Spanish: Jabirú Africano.

physical characteristics

Length 55–59 in (140–150 cm), wingspan 94–106 in (240–270 cm); 11–16.1 lb (5–7.3 kg). One of the largest storks. Mostly

orange/red bill divided by a black band, surmounted by patch of yellow. Black neck and flight feathers, white body feathers; dark legs with red "knees." Males and females differ both in size (the male is larger) and iris color (brown in male, yellow in female).

distribution

Tropical Africa south of the Sahara.

habitat

Open wetlands.

behavior

Mostly solitary. Flies with heavy wing-beats and neck outstretched; makes use of thermals.

feeding ecology and diet

Mainly fish. Hunts by sight and, occasionally, touch.

reproductive biology

Monogamous. Nests alone toward end of rainy season. Nest a platform of sticks. Clutch size two to three eggs, incubation 30–35 days, fledging 70–100 days.

conservation status

Not threatened.

significance to humans

Popular with ecotourists on wildlife holidays in East Africa.

Jabiru

Jabiru mycteria

subfamily

Tribe Leptoptilini

taxonomy

Ciconia mycteria Lichtenstein, 1819. Monotypic.

other common names

English: American jabiru, jabiru stork; French: Jabiru d'Amérique; German: Jabiru; Spanish: Jabirú Americano.

physical characteristics

Length 48–55 in (122–140 cm), wingspan 90–102 in (230–260 cm); weight 17.6 lb (8 kg). Mostly white with dark bill and neck, colored red at base.

distribution

Tropical Central and South America to northern Argentina.

habitat

Freshwater wetlands.

behavior

May retract neck in flight due to having heavy bill that, if outstretched, would cause problems with balance.

feeding ecology and diet

Fish and other aquatic animals. Uses both sight and touch to locate prey. Will splash bill in shallow water to disturb prey prior to capture.

reproductive biology

Nests alone or in small groups in trees. Nests are large platforms of sticks and mud, may be built upon season after season. Clutch size three to four eggs, fledging 80–95 days.

conservation status

Not threatened.

significance to humans

Hunted for food in some areas.

Marabou

Leptoptilos crumeniferus

subfamily

Tribe Leptoptilini

taxonomy

Ciconia crumenifera Lesson, 1831. Monotypic.

other common names

English: Marabou stork; French: Marabout d'Afrique; German: Marabu; Spanish: Marabú Africano.

physical characteristics

Length 3.3–5 ft (115–152 cm), wingspan 7.4–9.4 ft (225–287 cm); 8.8–19.6 lb (4–8.9 kg). Black and white, with featherless pink neck spotted black, and heavy greenish yellow bill.

distribution

Tropical Africa south of the Sahara.

habitat

Arid or semiarid open country within flying distance of rivers and lakes.

behavior

Fairly social, colonial during breeding season. Feeds in flocks, often with other species such as vultures. Voice a variety of whistles, clatters bill as display prior to mating.

feeding ecology and diet

Wide variety of animals including fish, reptiles, amphibians, and invertebrates; also carrion.

reproductive biology

Long breeding period, starting in the dry season through sub-sequent rains. Nest in trees, woven from sticks and lined with softer plant material. Clutch size two to three eggs, incubation 29–31 days, fledging after 95 days.

conservation status

Not globally threatened.

significance to humans

Scavenge on carrion from waste dumps and other areas around human settlements.

Resources

Books

Collar, N. J., M. J. Crosby, and A. J. Stattersfield. Birds to Watch 2: The World List of Threatened Birds. Cambridge: BirdLife International, 1994.

del Hoyo, J., A. Elliot, and J. Sargatal, eds. Handbook of the Birds of the World. Vol. 1, Ostrich to Ducks. Barcelona: Lynx Edicions, 1992.

Hancock, J. A., J. A. Kushlan, and M. P. Kahl. Storks, Ibises and Spoonbills of the World. London: Academic Press, 1992.

Snow, David, and Christopher M. Perrins, eds. Birds of the Western Palearctic: Concise Edition. Oxford: Oxford University Press, 1997.

Organizations

BirdLife International. Wellbrook Court, Girton Road, Cambridge, Cambridgeshire CB3 0NA United Kingdom. Phone: +44 1 223 277 318. Fax: +44-1-223-277-200. E-mail: [email protected] Web site: <http://www.birdlife.net>

Tony Whitehead, BSc