The wood stork (Mycteria americana) is a large wading bird in the family Ciconiidae (storks). Originally described in 1758 by Carl Linnaeus, this stork is native to the subtropics and tropics of the Americas where it persists in habitats with fluctuating water levels. It is the only stork species that breeds in North America. 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.

Globally, the wood stork is considered to be of least concern by the International Union for Conservation of Nature. In the United States, the wood stork was previously classified as Endangered due to loss of suitable feeding habitat in the Florida Everglades, its historical population stronghold in the country. The species has been subsequently downlisted to Threatened after northward range expansion and increased population size.

Taxonomy and etymology

The wood stork was first formally given its binomial name Mycteria americana by Linnaeus in 1758. Linnaeus originally named two separate species, M. americana and Tantalus loculator, based on different and slightly erroneous accounts, in his book Systema Naturae. It was later identified that these binomials referred to the same species, making M. americana and T. loculator synonymous. M. americana takes priority as it occurs before T. loculator.

The accepted genus name Mycteria derives from the Greek μυκτήρ : myktēr, meaning snout or trunk, and the species name americana references the distribution of this stork. It also has been given the name of the "American wood stork", because it is found in the Americas.

The wood stork is classified within the tribe Mycteriini (which encompasses all species of genera Anastomus and Mycteria) based on morphology and behaviour.

Description

left|upright|thumb|The wood stork's head much resembles that of an [[ibis.]]

The adult wood stork is a large bird which stands tall with a wingspan of . The male typically weighs , with a mean weight of ; the female weighs , with a mean weight of . Another estimate puts the mean weight at . 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 , , and tail being black and having a greenish and purplish iridescence. The legs and feet are dark, and the pink/beige-coloured toes are pink during the breeding season. The sexes are similar.

Newly hatched chicks have a sparse coat of grey down () that is replaced by a dense, wooly, and white down () 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.

Within the United States, small breeding populations exist in Florida, Georgia, and the Carolinas.

In Mexico, non-breeding birds can be found along both the Pacific and Atlantic coasts, while breeding colonies are restricted to the Pacific coast. Most descriptions of wood stork breeding colonies in western Mexico are over 35 years old, but recent sources have confirmed active nesting colonies in the southwestern states of Oaxaca and Colima. Both colonies exist in important wetlands - Zapata Swamp and the Sabana-Camaguey Archipelago. Outside of Cuba, sightings of wood storks are rare in the Caribbean as the birds were extirpated from Hispaniola and are vagrants on other Caribbean islands.

In South America, the wood stork is found south to northern Argentina. Most breeding colonies in Brazil are concentrated in the Pantanal wetland and the northern coastal region. Birds that breed in west-central Brazil often disperse to southern Brazil and northern Argentina after breeding.

The wood stork is able to adapt to a variety of tropical and subtropical wetland habitats 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 US), while in estuaries, it generally nests on trees in the mangrove forests. 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. For Taxodium trees, it generally nests near the top branches, frequently between above the ground.

The nest itself is built by the male When complete, the nest is about in diameter,

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.thumb|Eggs of the wood stork|300x300pxThis bird lays one clutch of three to five cream coloured eggs that are about in size. by both sexes. The eggs hatch in the order in which they were laid, with an interval of a few days between when each egg hatches. and reach sexual maturity at four years of age, although they usually do not successfully fledge chicks until their fifth year of age. Overall, about 31% of nests produce at least one fledged bird. The wood stork eats larger fish more often than smaller fish, even in some cases where the latter is more abundant. It is estimated that an adult wood stork needs about per day to sustain itself. For a whole family, it is estimated that about are needed per breeding season.

Both parents feed the chicks by regurgitating food onto the nest floor. The chicks are mainly fed fish that are between in length, with the length of the fish typically 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 before it fledges. especially during dry periods where the water beneath nesting trees dries up. Other species of Haemoproteus also infect wood storks in Costa Rica, in addition to Syncuaria mycteriae, a nematode found in the gizzard of the wood stork.

In Florida, wood storks may be eaten by some growth stage of invasive snakes such as Burmese pythons, reticulated pythons, Central African rock pythons, Southern African rock pythons, boa constrictors, yellow anacondas, Bolivian anacondas, dark-spotted anacondas, and green anacondas.

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 through continuously flapping its wings. It can then glide for distances ranging from . It does not have to flap its wings during this time because the warm thermals are strong enough to support its weight.

Excretion and thermoregulation

thumb|A wood stork shading its young|450x450px|left

During the breeding season, the wood stork commonly defecates over the edge of its nest, while the chicks usually defecate inside. In hot weather, breeding adults will also shade their chicks with their wings.

Phylogenetics

  • Wood stork – Mycteria americana – USGS Patuxent Bird Identification InfoCenter
  • Florida Bird Sounds at Florida Museum of Natural History