AppearanceThe adult wood stork is a large bird which stands 83 to 115 cm tall with a wingspan of 140 to 180 cm. The male typically weighs 2.5 to 3.3 kg, with a mean weight of 2.7 kg; the female weighs 2.0 to 2.8 kg, with a mean weight of 2.42 kg.
Another estimate puts the mean weight at 2.64 kg. 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.
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.
NamingThe wood stork was first formally described and given its binomial name ''Mycteria americana'' by Linnaeus in 1758. Linnaeus based his description on a misplaced account and illustration in ''Historia Naturalis Brasiliae'' 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.
DistributionThis 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. In South America, it is found south to northern Argentina. Some populations in North America disperse after breeding, frequently to South America.
StatusGlobally, the wood stork is considered least concern by the International Union for Conservation of Nature due to its large range. 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 caused by habitat loss and drought. 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. 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.
HabitatThis stork is able to adapt to a variety of tropical and subtropical wetland habitats having fluctuating water levels. 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'', 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.
ReproductionA resident breeder in lowland wetlands with trees, the wood stork builds a large stick nest in a tree. In freshwater habitats, it prefers to nest in trees that are larger in diameter. It nests colonially, with up to 25 nests in one tree. The height of these nests is variable, with some nests located in shorter mangrove trees being at heights of about 2.5 metres, compared to a height of about 6.5 metres for taller mangrove trees. For ''Taxodium'' trees, it generally nests near the top branches, frequently between 18 and 24 metres above the ground. On the tree itself, forks of large limbs or places where multiple branches cross are usually chosen.
The nest itself is built by the male from sticks and green twigs collected from the colony and the surrounding area. 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. When complete, the nest is about one metre in diameter, with a central green area having an average diameter of about 28 centimetres. The thickness of the edge of the nest usually measures from 12 to 20 centimetres.
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.
FoodDuring 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.
PredatorsRaccoons are predators of wood stork chicks, especially during dry periods where the water beneath nesting trees dries up. 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.
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