stork

[Middle English, from Old English storc.]

For more information on stork, visit Britannica.com.

(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

Resources

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.

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: birdlife@birdlife.org.uk Web site:

[Article by: Tony Whitehead, BSc]

The whimsical idea that storks bring babies, universally known in 20th-century England, must have been adopted from northern Europe, where storks nesting on roofs are regarded as a sign of good luck and family happiness.

Dansk (Danish)
n. - stork

Nederlands (Dutch)
ooievaar

Français (French)
n. - cigogne

Deutsch (German)
n. - Storch

Ελληνική (Greek)
n. - (ορνιθ.) λελέκι, πελαργός, (μτφ.) γεννητούρια

Italiano (Italian)
cicogna

Português (Portuguese)
n. - cegonha (f)

Русский (Russian)
аист

Español (Spanish)
n. - cigüeña

Svenska (Swedish)
n. - stork

中文（简体）(Chinese (Simplified))
鹳

中文（繁體）(Chinese (Traditional))
n. - 鸛

한국어 (Korean)
n. - 황새

日本語 (Japanese)
n. - コウノトリ

العربيه (Arabic)
‏(الاسم) لقلق, طائر طويل الساقين‏

עברית (Hebrew)
n. - ‮חסידה‬

If you are unable to view some languages clearly, click here.

To select your translation preferences click here.