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Lifespan, longevity, and ageing

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Maximum longevity: 27 years (captivity) Observations: One captive animal lived for 27 years (Brouwer et al. 1992).
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Reproduction

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Wood storks are monogamous.

Mating System: monogamous

Pairs often mate for life and return to the same nest each breeding season to raise their offspring. Breeding occurs from December to April. Nests are constructed out of sticks high atop cypress, mangrove, or other trees in marshy woodlands. Wood storks nest colonially with from 5 to 25 nests in a single tree.

Females lay 2 to 4 (usually 3) eggs per clutch. Incubation lasts 28 to 32 days and the young fledge after 55 to 60 days. Woodstorks do not begin to breed until they are 4 years old.

Breeding season: December to April

Range eggs per season: 2 to 4.

Range time to hatching: 28 to 32 days.

Range fledging age: 55 to 60 days.

Average age at sexual or reproductive maturity (female): 4 years.

Average age at sexual or reproductive maturity (male): 4 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous

Average eggs per season: 3.

Both the male and female take part in nest building, incubation and the feeding of their semi-altricial young. Chicks are fed regurgitated fish and are dependent on their parents for 55 to 60 days after they hatch.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female)

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Untitled

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Wood storks are the only nesting storks in the United States and our largest wading bird. They are also endearingly called "flinthead" or "ironhead" by some.

Traditionally in Austrian and German folklore, storks were said to deliver babies. These stories have now been passed on to the Americas. Wood storks are exceptionally serene animals that can live harmoniously alongside humans if left undisturbed.

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Behavior

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Like other migrating birds, wood storks may locate their nesting grounds by recognizing geographical landmarks and sensing magnetic fields.

Perception Channels: visual ; tactile ; acoustic ; chemical ; magnetic

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Conservation Status

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In the 1930's an estimated 20,000 wood stork pairs were nesting in the United States. In 1978 only 2,500 pairs were recorded and wood storks were placed on the Endangered Species List in 1984. A recent survey of nesting pairs counted 5,500 pairs (Klinkenberg, 1998). If the species grows to 6,000 nesting pairs it may be reclassified to "threatened" instead of "endangered". The best way to help the species is to preserve wetlands, limit water management, and reduce heavy metal pollution such as mercury which can be lethal to the storks (Bryan et al., 2001a).

Historically the largest American population of wood storks has been in Florida's Big Cypress National Preserve and the Everglades, but because of a decline in wetland habitat and water management, colonies seem to be migrating northward (Brooks, 2001).

Wood storks are listed as endangered on the US Federal List and are protected under the US MBTA.

US Migratory Bird Act: protected

US Federal List: endangered

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Life Cycle

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The eggs are incubated for one month and the newborn chicks hatch weighing only 57 grams. They are completely helpless except for the feathered umbrella that the parents provide with their wings to shield them from heat and rain (Klinkenberg 1998). There is sibling competition for food and under stressful conditions only the first-born and largest will survive. During times of heavy rains, nestlings often die or are deserted by their parents (Ramo and Busto 1992).

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Benefits

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There are no known adverse affects of wood storks on humans.

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Benefits

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We do not have information on economic importance for this species at this time.

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Associations

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Wood storks and other wading birds are an integral part of the marshland food chain along with other reptilian and mammalian predators.

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Trophic Strategy

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Adult wood storks eat small fish, frogs, mollusks, snails, insects, and aquatic invertebrates. It has been calculated that a 2.5 kilogram bird would eat more than half a kilogram of fish daily. Wood storks wade through shallow water feeling for movement and snap their bill shut when they touch a fish. Vision is not as important as touch, and the bill-snapping reflex of the stork is one of the fastest reflexes known in vertebrates, taking only about 25 thousandths of a second (Wolkomir and Wolkomir, 2001). It was also recently discovered that wood storks often leave the roost at night to catch prey or fish during nocturnal low tides. This allows them to feed without the competition of other large shorebirds such as great egrets.

Animal Foods: amphibians; fish; insects; mollusks

Primary Diet: carnivore (Piscivore )

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Distribution

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Mycteria americana range from North America to Argentina. In the United States, wood storks nest in South Carolina, Georgia, and Florida. After breeding they may disperse north to North Carolina or west to Mississippi and Alabama.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Habitat

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Wood storks inhabit mainly tidal waters, marshes, swamps, streams and mangroves. They hunt for prey in shallow, muddy-bottomed banks or wetlands. Their nests are ideally constructed in trees surrounded by water to limit depredation of the eggs.

Habitat Regions: temperate ; tropical ; terrestrial

Aquatic Biomes: brackish water

Wetlands: marsh ; swamp

Other Habitat Features: estuarine

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Life Expectancy

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We do not have information on lifespan/longevity for this species at this time.

Average lifespan
Status: wild:
225 months.

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Morphology

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Adults usually measure one meter tall and can have a wingspan of over one and a half meters. They have a blackish bill, accompanied with a scaly-looking, featherless head and neck which sticks out straight when flying. The majority of the birds' body is white except for the primary, secondary, and tail feathers which are black. Immature wood storks have a pale yellow bill and dull gray-colored head and neck.

Average length: 1 m.

Average wingspan: 1.5 m.

Other Physical Features: endothermic ; bilateral symmetry

Average mass: 2500 g.

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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Associations

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The greatest threat to wood storks are raccoons (Procyon lotor) that climb to the nests to eat the chicks. Alligators (Alligator mississippiensis) may also pose a problem to unwary birds.

Known Predators:

  • raccoons (Procyon lotor)
  • American alligators (Alligator mississippiensis)
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Carroll, S. 2002. "Mycteria americana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mycteria_americana.html
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Sean Carroll, Western Maryland College
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Randall L. Morrison, Western Maryland College
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Alaine Camfield, Animal Diversity Web
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Mycteria americana

provided by DC Birds Brief Summaries

A large (34-47 inches) wader, the Wood Stork is most easily identified by its white body, black wing edges, and large bald head. In flight, this species is easily separated from cranes by its short neck, from egrets by its ability to hold its neck extended in flight (as opposed to folding it back on its body), and from ibises by its extremely long legs. In fact, with its bald head and soaring flight, this species is more easily mistaken for a vulture than for any wader. Male and female Wood Storks are similar to one another in all seasons. The Wood Stork primarily breeds in the American tropics from southern Mexico and the Caribbean south to tropical portions of South America. In North America, this species is a local breeder and uncommon winter resident from south Florida north to coastal South Carolina. Non-breeding and post-breeding birds may wander widely during late summer, when they may turn up as far north as the Mid-Atlantic region and New England. Wood Storks breed in freshwater and brackish wetlands surrounded by trees, which this species uses to nest and roost colonially. In the non-breeding season, this species may be found in a number of wetland habitats ranging in size from large expanses of marshland to small ponds and canals. Wood Storks primarily eat small fish, but may also eat small quantities of insects and other small animals when available. Wood Storks may be best observed wading in shallow water, where they may be seen plunging their bills into the water to catch fish. It is also possible to see Wood Storks at their nest trees, especially when they return to roost at sunset, or while soaring singly or in small groups high above marshland. Wood Storks are primarily active during the day.

Threat Status: Least Concern

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Reid Rumelt

Mycteria americana

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A large (34-47 inches) wader, the Wood Stork is most easily identified by its white body, black wing edges, and large bald head. In flight, this species is easily separated from cranes by its short neck, from egrets by its ability to hold its neck extended in flight (as opposed to folding it back on its body), and from ibises by its extremely long legs. In fact, with its bald head and soaring flight, this species is more easily mistaken for a vulture than for any wader. Male and female Wood Storks are similar to one another in all seasons. The Wood Stork primarily breeds in the American tropics from southern Mexico and the Caribbean south to tropical portions of South America. In North America, this species is a local breeder and uncommon winter resident from south Florida north to coastal South Carolina. Non-breeding and post-breeding birds may wander widely during late summer, when they may turn up as far north as the Mid-Atlantic region and New England. Wood Storks breed in freshwater and brackish wetlands surrounded by trees, which this species uses to nest and roost colonially. In the non-breeding season, this species may be found in a number of wetland habitats ranging in size from large expanses of marshland to small ponds and canals. Wood Storks primarily eat small fish, but may also eat small quantities of insects and other small animals when available. Wood Storks may be best observed wading in shallow water, where they may be seen plunging their bills into the water to catch fish. It is also possible to see Wood Storks at their nest trees, especially when they return to roost at sunset, or while soaring singly or in small groups high above marshland. Wood Storks are primarily active during the day.

References

  • Coulter, M. C., J. A. Rodgers, J. C. Ogden and F. C. Depkin. 1999. Wood Stork (Mycteria americana), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/409
  • Mycteria americana. Xeno-canto. Xeno-canto Foundation, n.d. Web. 20 July 2012.
  • Wood Stork (Mycteria americana). The Internet Bird Collection. Lynx Edicions, n.d. Web. 20 July 2012.
  • eBird Range Map - Wood Stork. eBird. Cornell Lab of Ornithology, N.d. Web. 20 July 2012.

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Rumelt, Reid B. Mycteria americana. June-July 2012. Brief natural history summary of Mycteria americana. Smithsonian's National Museum of Natural History, Washington, D.C.
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Robert Costello (kearins)
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Wood stork

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The wood stork (Mycteria americana) is a large American wading bird in the stork family Ciconiidae. It was formerly called the "wood ibis", though it is not an ibis. It is found in subtropical and tropical habitats in the Americas, including the Caribbean. In South America, it is resident, but in North America, it may disperse to as far as South America. Originally described by Carl Linnaeus in 1758, this stork likely evolved in tropical regions. The head and neck are bare of feathers and dark grey in colour. The plumage is mostly white, with the exception of the tail and some of the wing feathers, which are black with a greenish-purplish sheen. The juvenile differs from the adult, with the former having a feathered head and a yellow bill, compared to the black adult bill. The sexes are similar.

The habitat of the wood stork can vary, but it must have a tropical or subtropical climate with fluctuating water levels. The one metre (3.3 ft) in diameter nest is found in trees, especially mangroves and those of the genus Taxodium, usually surrounded by water or over water. The wood stork nests colonially. The nest itself is made from sticks and greenery. During the breeding season, which is initiated when the water levels drop and can occur anytime between November and August, a single clutch of three to five eggs is laid. These are incubated for around 30 days, and the chicks hatch altricial. They fledge 60 to 65 days after hatching, although only about 31% of nests fledge a chick in any given year, with most chicks dying during their first two weeks, despite being watched by an adult during that time. The chicks are fed fish of increasing size. The diet of the adult changes throughout the year. During the dry season, fish and insects are eaten, compared to the addition of frogs and crabs during the wet season. Because it forages by touch, it needs shallow water to effectively catch food. This is also the reason why the wood stork breeds when water levels start to fall.

Globally, the wood stork is considered to be of least concern by the International Union for Conservation of Nature. This is due to its large range. In the United States, on the other hand, it is considered to be threatened. Predators of the wood stork include raccoons, which predate chicks, northern crested caracaras, which prey on eggs, and other birds of prey, which feed on both eggs and chicks. Hunting and egg-collecting by humans has been implicated as a factor in the decline of South American wood storks. Humans also cause nest failures through ecotourism, although observation through binoculars about 75 metres (246 ft) away does not have a large effect on nesting success. In both North and South America, habitat alteration has caused the wood stork to decline, with levee and drainage systems in the Everglades causing a shift in the timing of breeding and thus a decrease in breeding success.

Taxonomy and etymology

The wood stork was first formally described and given its binomial name Mycteria americana by Linnaeus in 1758.[2] Linnaeus based his description on a misplaced account and illustration in Historia Naturalis Brasiliae (1648)[3] of the jabiru-guacu. Linnaeus also described Tantalus loculator, which was proven to also apply to the jabiru-guacu, after M. americana based on a 1731 illustration of the wood stork by Mark Catesby under the name of wood pelican.[4] Since these binomials referred to the same species, M. americana and T. loculator are synonymous but M. americana takes priority as it occurs before T. loculator.[5] The accepted genus name derives from the Greek mykter, meaning snout, and the species name references the distribution of this stork.[6]

   

Wood stork

     

Yellow-billed stork

     

Milky stork

   

Painted stork

        Relationships of extant Mycteria[7]

This species seems to have evolved in tropical regions; its North American presence probably postdates the last ice age. A fossil fragment from the Touro Passo Formation found at Arroio Touro Passo (Rio Grande do Sul, Brazil) might be of the living species; it is at most from the Late Pleistocene age, a few 10,000s of years ago.[8] North American fossils from that time are of an extinct larger relative, M. wetmorei, which would be distinguished from the wood on the basis of size and on the basis of M. wetmorei's less curved mandible. This was probably a sister species; both occurred sympatrically on Cuba at the end of the Pleistocene.[9] Of the extant members of the genus Mycteria, this bird is basal to the clade yellow-billed stork, which is itself basal to the milky stork and the painted stork. This phylogeny is based on a 1996 study that sequenced the B chromosome and then utilized DNA–DNA hybridization to find the relations between the storks.[7]

Likely because of its decurved bill, the wood stork has formerly been called the "wood ibis", although it is not an ibis.[10] It also has been given the name of the "American wood stork", because it is found in the Americas.[11] Regional names include "flinthead", "stonehead", "ironhead", "gourdhead", and "preacher".[6]

Description

 src=
The wood stork's head much resembles that of an ibis

The adult wood stork is a large bird which stands 83 to 115 cm (33–45 in) tall with a wingspan of 140 to 180 cm (55–71 in). The male typically weighs 2.5 to 3.3 kg (5.5–7.3 lb), with a mean weight of 2.7 kg (6.0 lb); the female weighs 2.0 to 2.8 kg (4.4–6.2 lb), with a mean weight of 2.42 kg (5.3 lb).[12][13] Another estimate puts the mean weight at 2.64 kg (5.8 lb).[14] The head and neck of the adult are bare, and the scaly skin is a dark grey. The black downward-curved bill is long and very wide at the base. The plumage is mostly white, with the primaries, secondaries, and tail being black and having a greenish and purplish iridescence. The legs and feet are dark, and the flesh-coloured toes are pink during the breeding season. The sexes are similar.[15]

 src=
Two wood stork chicks at their nest

Newly hatched chicks have a sparse coat of grey down (protoptiles) that is replaced by a dense, wooly, and white down (mesoptiles) in about 10 days. Chicks grow fast, being about half the height of adults in three to four weeks. By the sixth and seventh weeks, the plumage on the head and neck turns smokey grey. When fledged, they resemble the adult, differing only in that they have a feathered head and a yellow bill.[16]

Distribution and habitat

This is a subtropical and tropical species which breeds in much of South America, Central America and the Caribbean. The wood stork is the only stork that breeds in North America. In the United States there are small breeding populations in Florida, Georgia, and the Carolinas.[17] In South America, it is found south to northern Argentina. Some populations in North America disperse after breeding, frequently to South America.[11]

This stork is able to adapt to a variety of tropical and subtropical wetland habitats[18] having fluctuating water levels (as that initiates breeding).[19] It nests in trees that are over water or surrounded by water. In freshwater habitats, it primarily nests in forests dominated by trees of the genus Taxodium (in the USA), while in estuaries, it generally nests on trees in the mangrove forests.[18] To feed, the wood stork uses freshwater marshes in habitats with an abundance of Taxodium trees, while in areas with mangrove forests, it uses brackish water. Areas with more lakes attract feeding on lake, stream, and river edges.[19]

Behaviour

Breeding

 src=
Nesting colony in Georgia, United States

A resident breeder in lowland wetlands with trees, the wood stork builds a large stick nest in a tree.[20] In freshwater habitats, it prefers to nest in trees that are larger in diameter.[18] It nests colonially, with up to 25 nests in one tree.[20] The height of these nests is variable, with some nests located in shorter mangrove trees being at heights of about 2.5 metres (8.2 ft), compared to a height of about 6.5 metres (21 ft) for taller mangrove trees.[21] For Taxodium trees, it generally nests near the top branches, frequently between 18 and 24 metres (59 and 79 ft) above the ground.[19] On the tree itself, forks of large limbs or places where multiple branches cross are usually chosen.[22]

The nest itself is built by the male[23] from sticks[24] and green twigs[25] collected from the colony and the surrounding area.[23] The greenery usually starts to be added before the eggs are laid but after the main structure of twigs is completed. The frequency at which it is added decreases after the eggs hatch. This greenery functions to help insulate the nest.[25] When complete, the nest is about one metre (3.3 ft) in diameter,[23] with a central green area having an average diameter of about 28 centimetres (11 in). The thickness of the edge of the nest usually measures from 12 to 20 centimetres (4.7 to 7.9 in).[22]

 src=
Wood storks copulating

Wood storks without a nest occasionally try to take over others' nests. Such nest take-overs are performed by more than one bird. The young and eggs are thrown out of the nest within about 15 minutes. If only one stork is attending the nest when it is forced out, then it usually waits for its mate to try to take the nest back over.[26]

Breeding is initiated by a drop in the water level combined with an increased density of fish (with the former likely triggering the latter). This is because a decrease in the water level and an increased density of fish allows for an adequate amount of food for the nestlings.[19] This can occur anytime between November and August. After it starts, breeding takes about four months to complete.[11] This bird lays one clutch of three to five cream coloured eggs that are about 68 by 46 millimetres (2.7 by 1.8 in) in size.[24] These eggs are usually laid one to two days apart[23] and incubated for 27 to 32 days[24] by both sexes.[23] This incubation period starts when the first egg is laid.[19] During the first week of incubation, the parents do not go far from the colony, with the exception of the short trips to forage, drink, and collect nesting material carried out by the non-incubating bird. After the first week, the non-incubating bird spends less time in the colony, although the eggs are never left unattended. After a few hours of incubation, this bird sometimes takes a break to stretch, preen itself, rearrange nest material, or turn the eggs.[23] The eggs hatch in the order in which they were laid, with an interval of a few days between when each egg hatches.[19]

 src=
Eggs of the wood stork

The chicks hatch altricial, unable to move, and weigh an average of 62 grams (2.2 oz).[16] They are brooded for the first week after hatching, and after that when it is raining and at night.[23] The chicks are not left alone until at least three weeks of age, with one parent foraging while the other guards the nest and chicks. When the chicks are at least three weeks old, they are large enough to stay and protect the nest. This coincides with the chicks getting more aggressive when presented with foreign objects or organisms. They fledge 60 to 65 days after hatching,[16] and reach sexual maturity at four years of age, although they usually do not successfully fledge chicks until their fifth year of age.[11]

The hatching success, the percentage of birds that had at least one egg that hatched in a year, of the wood stork is around 62%. This can vary widely, though, with colonies ranging from about 26% to 89% hatching success. The period when chicks are most vulnerable to death is from hatching to when they are two weeks old.[27] Overall, about 31% of nests produce at least one fledged bird.[22] Raccoons[11] and caracaras, especially northern crested caracaras, are prominent predators of eggs and chicks. Other causes of nesting failure is the falling of nests, thus breaking the eggs inside. This can be caused by many events, the most prominent being poor nest construction and fights between adults.[22]

Feeding

During the dry season, the wood stork eats mostly fish, supplemented by insects. During the wet season, on the other hand, fish make up about half the diet, crabs make up about 30%, and insects and frogs make up the rest.[28] The wood stork eats larger fish more often than smaller fish, even in some cases where the latter is more abundant.[29] It is estimated that an adult wood stork needs about 520 grams (1.15 lb) per day to sustain itself. For a whole family, it is estimated that about 200 kilograms (440 lb) are needed per breeding season.[19]

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A wood stork foraging

The wood stork usually forages in flocks when not breeding, and alone and in small groups when it is breeding. In the dry season, this bird generally forages by slowly walking forward with its bill submerged in the water while groping for food. During the wet season, this method is used about 40% of the time to catch food. During this period, foot stirring, where the stork walks very slowly with the bill in water while pumping its foot up and down before every step, is used about 35% of the time. Both these hunting methods are non-visual.[28]

Because of its non-visual foraging methods, the wood stork requires shallow water and a high density of fish to forage successfully. The water that it forages in during the dry season averages about 17 centimetres (6.7 in) in depth, while during the wet season, the water usually is about 10 centimetres (3.9 in) deep. In the dry season, this stork prefers to forage in waters with no emergent vegetation, whereas in the wet season, it prefers areas with vegetation emerging between 10 and 20 centimetres (3.9 and 7.9 in) above the surface on average.[28] This bird can travel over 80 kilometres (50 mi) to reach foraging sites, lending it access to a wide variety of habitats.[30]

Both parents feed the chicks by regurgitating food onto the nest floor. The chicks are mainly fed fish that are between 2 and 25 centimetres (0.79 and 9.84 in) in length, with the length of the fish usually increasing as the chicks get older. The amount of food that the chicks get changes over time, with more being fed daily from hatching to about 22 days, when food intake levels off. This continues until about 45 days, when food consumption starts to decrease. Overall, a chick eats about 16.5 kilograms (36 lb) before it fledges.[16]

Flight

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A wood stork in flight

When flying, this bird utilizes two different techniques. When it is not sufficiently warm and clear, such as in the late afternoon or on cloudy days, this stork alternates between flapping its wings and gliding for short periods of time. When it is warm and clear, this bird glides after it gains an altitude of at least 610 metres (2,000 ft) through continuously flapping its wings. It can then glide for distances ranging from 16 to 24 kilometres (9.9 to 14.9 mi). It does not have to flap its wings during this time because the warm thermals are strong enough to support its weight.[19] Because of the energy that is conserved by soaring, this stork usually uses this method to fly to more distant areas.[31] It flies with its neck outstretched and its legs and feet trailing behind it.[15]

When flying to foraging areas, the wood stork averages a speed of about 24.5 kilometres per hour (15.2 mph). In flapping flight it does 34.5 kilometres per hour (21.4 mph), and about 20 kilometres per hour (12 mph) by gliding.[31]

Excretion and thermoregulation

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A wood stork shading its young

During the breeding season, the wood stork commonly defecates over the edge of its nest, while the chicks usually defecate inside.[25] The method of defecation of the adult differs based on temperature. Normally, it excretes by leaning forward and slightly raising its tail, with the waste either going straight down or slightly backwards. When it is hot, though, the adult takes a different position, quickly moving its tail downwards and forwards while twisting its body around to aim at a leg that is bent backwards (this is called urohidrosis). Which leg is aimed at is alternated. The excrement aimed at the legs is fluid and watery. It generally hits the legs around the middle of the unfeathered tibia, and runs down the leg as it is being directed by the scales. This results in evaporation, making this a method of thermoregulation. The temperature at which this starts is slightly above the threshold for panting, the latter of which takes place at temperatures of about 41.7 °C (107.1 °F) and above, compared to the normal body temperature of about 40.7 °C (105.3 °F).[32] In hot weather, breeding adults will also shade their chicks with their wings.[25]

Predators and parasites

Raccoons are predators of wood stork chicks,[33] especially during dry periods where the water beneath nesting trees dries up.[11] Where it occurs, the crested caracara is a significant predator of eggs. Other caracaras, and hawks and vultures, also prey on both eggs and chicks.[22]

In the United States, Haemoproteus crumenium, a blood protozoan, can be found in subadult and adult wood storks.[34] Other species of Haemoproteus also infect wood storks in Costa Rica,[35] in addition to Syncuaria mycteriae, a nematode found in the gizzard of the wood stork.[36]

Status

Globally, the wood stork is considered least concern by the International Union for Conservation of Nature due to its large range.[1] In the United States, this bird is considered to be threatened. This is a recovery from its former status as endangered, which it held from 1984 to 2014 because of a decline in its population[17] caused by habitat loss and drought.[37] Similarly, in the state of Santa Catarina, Brazil, its decline seems to have been reversed: after an absence between the late 1960s and the mid-1990s, the species is now again regularly encountered there, in particular in the Tubarão River region.[38] It is likely that the Paraná River region's wetlands served as a stronghold of the species, from where it is now re-colonizing some of its former haunts.[39]

Threats Disturbance by tourists can have an effect on nesting success, with a study finding that nests that had boats passing by them within about 20 metres (66 ft) had an average of 0.1 chicks fledging, compared to the normal rate for that area of about 0.9 chicks fledging per nest. Pedestrians watching from a distance of at least 75 metres (246 ft) did not significantly affect nesting success.[40] In the Everglades, levee and drainage systems have caused the timing of water fluctuations to change, thus shifting the timing of nesting and consequently a decrease in population.[30]

References

  1. ^ a b BirdLife International (2012). "Mycteria americana". IUCN Red List of Threatened Species. IUCN. 2012. Retrieved 26 November 2013.old-form url
  2. ^ Linnaeus, Carl (1758). Systema Naturæ per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis (in Latin). Volume 1 (10th ed.). Holmiae (Stockholm): Laurentii Salvii. p. 140.
  3. ^ Piso, Willem; Marcgraf, Georg (1648). Historia Naturalis Brasiliae (in Latin). pp. 200–202.
  4. ^ Catesby, Mark (1731). The Natural History of Carolina, Florida and the Bahama Islands. 1. London: Printed at the expence of the author, and sold by W. Innys and R. Manby, at the West End of St. Paul's, by Mr. Hauksbee, at the Royal Society House, and by the author, at Mr. Bacon's in Hoxton. p. 80.
  5. ^ Allen, J.A. (1908). "The generic names Mycteria and Tantalus of Linnaeus, 1758" (PDF). The Auk. 25 (1): 37–38. doi:10.2307/4070247. hdl:2027/hvd.32044107327066. JSTOR 4070247.
  6. ^ a b Nellis, David W. (March 2001). Common Coastal Birds of Florida and the Caribbean. Sarasota: Pineapple Press. p. 150. ISBN 978-1-56164-191-8.
  7. ^ a b Sheldon, Frederick H.; Slikas, Beth (1997). "Advances in Ciconiiform systematics 1976-1996". Colonial Waterbirds. 20 (1): 106–114. doi:10.2307/1521772. ISSN 0738-6028. JSTOR 1521772.
  8. ^ Schmaltz Hsou, Annie (2007). "O estado atual do registro fóssil de répteis e aves no Pleistoceno do Estado do Rio Grande do Sul, Brasil" [The current state of the fossil record of Pleistocene reptiles and birds of Rio Grande do Sul]. Quaternário do RS: Integrando Conhecimento (in Portuguese): 23–24.
  9. ^ Suárez, William; Olson, Storrs L. (2003). "New records of storks (Ciconiidae) from Quaternary asphalt deposits in Cuba". The Condor. 105 (1): 150–154. doi:10.1650/0010-5422(2003)105[150:NROSCF]2.0.CO;2. hdl:10088/1553.
  10. ^ Yow, John (1 May 2012). The Armchair Birder Goes Coastal: The Secret Lives of Birds of the Southeastern Shore. Chapel Hill: University of North Carolina Press. p. 75. ISBN 978-0-8078-8260-3.
  11. ^ a b c d e f Elliott, Andrew; Garcia, E.F.J.; Kirwan, G.M.; Boesman, P. (2017). del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi; Christie, David A.; de Juana, Eduardo (eds.). "Wood Stork (Mycteria americana)". Handbook of the Birds of the World Alive. Barcelona, Spain: Lynx Edicions. Retrieved 26 August 2017.
  12. ^ Brant, Heather A; Jagoe, Charles H; Snodgrass, Joel W.; Bryan, A. Lawrence; Gariboldi, Joan C (2002). "Potential risk to wood storks (Mycteria americana) from mercury in Carolina Bay fish". Environmental Pollution. 120 (2): 405–413. doi:10.1016/S0269-7491(02)00112-4. ISSN 0269-7491.
  13. ^ CRC Handbook of Avian Body Masses, 2nd Edition by John B. Dunning Jr. (Editor). CRC Press (2008). ISBN 978-1-4200-6444-5.
  14. ^ Palmer, R. S. (1962). Handbook of North American birds, Volume 1, Loons through Flamingos. Yale Univ. Press, New Haven, CT.
  15. ^ a b Coulter, M. C.; Rodgers, J. A.; Ogden, J. C.; Depkin, F. C.; Poole, A.; Gill, F. (1999). "Wood Stork (Mycteria americana)". The Birds of North America Online. doi:10.2173/bna.409. Retrieved 24 November 2017.
  16. ^ a b c d Kahl, M. Philip (1962). "Bioenergetics of growth in nestling wood storks" (PDF). The Condor. 64 (3): 169–183. doi:10.2307/1365200. ISSN 0010-5422. JSTOR 1365200.
  17. ^ a b "Wood stork off endangered list after recovery in U.S. Southeast". Reuters. 26 June 2014. Retrieved 1 July 2014.
  18. ^ a b c Rodgers, James A.; Schwikert, Stephen T.; Shapiro-Wenner, Anne (1996). "Nesting habitat of wood storks in north and central Florida, USA". Colonial Waterbirds. 19 (1): 1. doi:10.2307/1521802. ISSN 0738-6028. JSTOR 1521802.
  19. ^ a b c d e f g h Kahl, M. Philip (1964). "Food ecology of the wood stork (Mycteria americana) in Florida" (PDF). Ecological Monographs. 34 (2): 97–117. doi:10.2307/1948449. ISSN 0012-9615. JSTOR 1948449. Archived from the original (PDF) on 2018-01-14. Retrieved 2018-01-14.
  20. ^ a b Ehrlich, Paul R.; Dobkin, David S.; Wheye, Darryl (1992). Birds in Jeopardy. Stanford, CA: Stanford University Press. p. 18. ISBN 978-0-8047-1967-4.
  21. ^ Llanes-Quevedo, Alexander; Rodríguez-Ochoa, Alejandro; Rodríguez, Carlos Frankel (2015). "Reproducción y hábitat de cría de Mycteria americana (Aves: Ciconiidae) en Cuba" [Reproduction and nesting habitat of Mycteria americana (Aves: Ciconiidae) in Cuba]. Revista Cubana de Ciencias Biológicas (in Spanish). 4 (1): 96–101.
  22. ^ a b c d e González, José A. (1999). "Nesting success in two wood stork colonies in Venezuela" (PDF). Journal of Field Ornithology. 70 (1): 18–27.
  23. ^ a b c d e f g Clark, E. Scott (1980). "The attentiveness and time budget of a pair of nesting wood storks". Proceedings of the Colonial Waterbird Group. 3: 204–215. ISSN 1556-5785. JSTOR 4626715.
  24. ^ a b c Hauber, Mark E. (1 August 2014). The Book of Eggs: A Life-Size Guide to the Eggs of Six Hundred of the World's Bird Species. Chicago: University of Chicago Press. p. 106. ISBN 978-0-226-05781-1.
  25. ^ a b c d Rodgers, James A.; Wenner, Anne S.; Schwikert, Stephen T. (1988). "The use and function of green nest material by wood storks" (PDF). The Wilson Bulletin. 100 (3): 411–423. ISSN 0043-5643. JSTOR 4162606.
  26. ^ Bryan, A. Lawrence; Coulter, Malcolm C. (1991). "Conspecific aggression in a wood stork colony in Georgia" (PDF). The Wilson Bulletin. 103 (4): 693–697. ISSN 0043-5643.
  27. ^ Rodgers, James A.; Schwikert, Stephen T. (1997). "Breeding success and chronology of wood storks Mycteria americana in northern and central Florida, U.S.A.". Ibis. 139 (1): 76–91. doi:10.1111/j.1474-919X.1997.tb04506.x. ISSN 0019-1019.
  28. ^ a b c González, José A. (1997). "Seasonal variation in the foraging ecology of the wood stork in the southern Llanos of Venezuela" (PDF). The Condor. 99 (3): 671–680. doi:10.2307/1370479. ISSN 0010-5422. JSTOR 1370479.
  29. ^ Ogden, John C.; Kushlan, James A.; Tilmant, James T. (1976). "Prey selectivity by the wood stork" (PDF). The Condor. 78 (3): 324. doi:10.2307/1367691. ISSN 0010-5422. JSTOR 1367691.
  30. ^ a b Kushlan, James A. (1986). "Responses of wading birds to seasonally fluctuating water levels: Strategies and their limits". Colonial Waterbirds. 9 (2): 155–162. doi:10.2307/1521208. ISSN 0738-6028. JSTOR 1521208.
  31. ^ a b Bryan, A. Lawrence; Coulter, Malcolm C. (1987). "Foraging flight characteristics of wood storks in east-central Georgia, U.S.A.". Colonial Waterbirds. 10 (2): 157. doi:10.2307/1521254. ISSN 0738-6028. JSTOR 1521254.
  32. ^ Kahl, M. Philip (1963). "Thermoregulation in the wood stork, with special reference to the role of the legs". Physiological Zoology. 36 (2): 141–151. doi:10.1086/physzool.36.2.30155437. ISSN 0031-935X.
  33. ^ Coulter, Malcolm C.; Bryan, A. Lawrence (1995). "Factors affecting reproductive success of wood storks (Mycteria americana) in east-central Georgia" (PDF). The Auk. 112 (1): 237–243. doi:10.2307/4088782. ISSN 0004-8038. JSTOR 4088782.
  34. ^ Zabransky, Cody J.; Webb, Stephen L.; Fedynich, Alan M.; Bryan, A. Lawrence (2008). "Blood parasites in wood storks (Mycteria americana) from the southeastern United States". Journal of Parasitology. 94 (5): 1178–1179. doi:10.1645/GE-1480.1. PMID 18576809.
  35. ^ Valkiūnas, Gediminas; Iezhova, Tatjana A.; Brooks, Daniel R.; Hanelt, Ben; Brant, Sara V.; Sutherlin, Marie E.; Causey, Douglas (2004). "Additional observations on blood parasites of birds in Costa Rica". Journal of Wildlife Diseases. 40 (3): 555–561. doi:10.7589/0090-3558-40.3.555. PMID 15465725.
  36. ^ Zhang, Luping; Brooks, Daniel R.; Causey, Douglas (2003). "A new species of Syncuaria Gilbert, 1927 (Nematoda: Acuarioidea: Acuariidae) in the wood stork, Mycteria americana L. (Aves: Ciconiiformes: Ciconiidae) from the Area de Conservacion Guanacaste, Costa Rica". Journal of Parasitology. 89 (5): 1034–1038. doi:10.1645/GE-3127. PMID 14627152.
  37. ^ Allen, Greg (3 February 2013). "All Things Considered". Wood Stork's Endangered Status Is Up In The Air (radio broadcast). NPR. Broadcast at 15:13 Eastern Time.
  38. ^ Amorim, James Faraco; Piacentini, Vítor de Queiroz (2006). "Novos registros de aves raras em Santa Catarina, Sul do Brasil, incluindo os primeiros registros documentados de algumas espécies para o Estado" [New records of rare birds, and first reports of some species, in the state of Santa Catarina, southern Brazil]. Revista Brasileira de Ornitologia (in Portuguese). 14 (2): 145–149.]
  39. ^ Bencke, Glayson Ariel (2007). "Avifauna atual do Rio Grande do Sul, Brasil: aspectos biogeográficos e distribucionais" [The recent avifauna of Rio Grande do Sul: Biogeographical and distributional aspects]. Quaternário do RS: Integrando Conhecimento (in Portuguese): 65–67.
  40. ^ Bouton, Shannon N.; Frederick, Peter C.; Rocha, Cristiano Dosualdo; Barbosa Dos Santos, Alexandre T.; Bouton, Tara C. (2005). "Effects of tourist disturbance on wood stork nesting success and breeding behavior in the Brazilian Pantanal". Waterbirds. 28 (4): 487–497. doi:10.1675/1524-4695(2005)28[487:EOTDOW]2.0.CO;2. ISSN 1524-4695.

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Wood stork: Brief Summary

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The wood stork (Mycteria americana) is a large American wading bird in the stork family Ciconiidae. It was formerly called the "wood ibis", though it is not an ibis. It is found in subtropical and tropical habitats in the Americas, including the Caribbean. In South America, it is resident, but in North America, it may disperse to as far as South America. Originally described by Carl Linnaeus in 1758, this stork likely evolved in tropical regions. The head and neck are bare of feathers and dark grey in colour. The plumage is mostly white, with the exception of the tail and some of the wing feathers, which are black with a greenish-purplish sheen. The juvenile differs from the adult, with the former having a feathered head and a yellow bill, compared to the black adult bill. The sexes are similar.

The habitat of the wood stork can vary, but it must have a tropical or subtropical climate with fluctuating water levels. The one metre (3.3 ft) in diameter nest is found in trees, especially mangroves and those of the genus Taxodium, usually surrounded by water or over water. The wood stork nests colonially. The nest itself is made from sticks and greenery. During the breeding season, which is initiated when the water levels drop and can occur anytime between November and August, a single clutch of three to five eggs is laid. These are incubated for around 30 days, and the chicks hatch altricial. They fledge 60 to 65 days after hatching, although only about 31% of nests fledge a chick in any given year, with most chicks dying during their first two weeks, despite being watched by an adult during that time. The chicks are fed fish of increasing size. The diet of the adult changes throughout the year. During the dry season, fish and insects are eaten, compared to the addition of frogs and crabs during the wet season. Because it forages by touch, it needs shallow water to effectively catch food. This is also the reason why the wood stork breeds when water levels start to fall.

Globally, the wood stork is considered to be of least concern by the International Union for Conservation of Nature. This is due to its large range. In the United States, on the other hand, it is considered to be threatened. Predators of the wood stork include raccoons, which predate chicks, northern crested caracaras, which prey on eggs, and other birds of prey, which feed on both eggs and chicks. Hunting and egg-collecting by humans has been implicated as a factor in the decline of South American wood storks. Humans also cause nest failures through ecotourism, although observation through binoculars about 75 metres (246 ft) away does not have a large effect on nesting success. In both North and South America, habitat alteration has caused the wood stork to decline, with levee and drainage systems in the Everglades causing a shift in the timing of breeding and thus a decrease in breeding success.

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