Wood Stork

## Description

The wood stork (Mycteria americana ) is a large American wading bird in the family Ciconiidae (storks), the only member of the family to breed in North America. 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 as far as Florida. 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. There is little sexual dimorphism.

The wood stork's habitat can vary, but it must have a tropical or subtropical climate with fluctuating water levels. The one-metre-diameter (3.3-foot) 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 decline 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 underdeveloped, or altricial, requiring support from their parents. 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 on chicks), crested caracaras, which prey on eggs, and other birds of prey, which feed on 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. 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.

## Appearance

The Wood stork is a large American wading bird that is found in subtropical and tropical wetlands in the Americas, including the Caribbean. The head and neck of the bird are bare of feathers and dark grey in color. 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 legs and feet are dark, and the flesh-colored toes are pink during the breeding season. The juvenile differs from the adult, with the former having a feathered head and a yellow bill, compared to the black adult bill. The male and the female in this species look similar.

## Distribution

Wood storks breed in North America, much of South America, Central America, and the Caribbean. In the United States, there are small breeding populations in Florida, Georgia, and the Carolinas. In South America, these birds are found south to northern Argentina. In South America they are resident but in North America, some populations disperse after breeding, frequently to South America. Wood storks are able to adapt to a variety of wetland habitats. They can be found in estuaries, mangrove forests, swamps, ponds, freshwater marshes, flooded farm fields, lakes, streams, and river edges.

## Behavior

Wood storks are gregarious birds that live in flocks and nest in large colonies. By day they usually forage in flocks when not breeding, and alone and in small groups when they are breeding. In the dry season, these birds generally forage by slowly walking forward with their bill submerged in the water while groping for food. During the wet season, Wood storks forage mainly by foot stirring, where they walk very slowly with the bill in the water while pumping the foot up and down before every step. Both these hunting methods are non-visual and because of this Wood storks require shallow water and a high density of fish to forage successfully. In the afternoon, these birds usually raise in the sky to soar on thermals. When it is warm and clear, they glide after they gain an altitude of at least 610 meters (2,000 ft) continuously flapping their wings. When it is not sufficiently warm and clear, such as in the late afternoon or on cloudy days, Wood storks alternate between flapping their wings and gliding for short periods of time. These birds are generally silent but sometimes they will make some croak or hiss like a snake.

## Diet

Wood storks are carnivores (piscivores, insectivores). During the dry season, they eat 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.

## Reproduction

Wood storks are serially monogamous and form pairs that stay together only for a single breeding season. Breeding occurs anytime between November and August and it takes about four months to complete. Wood storks nest colonially in trees that are over water or surrounded by water, with up to 25 nests in one tree. 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. This greenery functions to help insulate the nest. The female lays one clutch of 3 to 5 cream-colored eggs which are incubated for 27 to 32 days by both parents. 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. The chicks hatch altricial, are unable to move, and weigh an average of 62 grams (2.2 oz). They are brooded for the first week after hatching, and after that when it is raining and at night. The chicks are not left alone until at least 3 weeks of age, with one parent foraging while the other guards the nest and chicks. When the chicks are at least 3 weeks old, they are large enough to stay and protect the nest. They fledge 60 to 65 days after hatching and reach reproductive maturity at 4 years of age.

## Population

### Population threats

Globally, Wood storks are not considered to be endangered, however, in the United States, on the other hand, they are considered to be threatened. This is caused by habitat loss, drought, as well as predation on eggs and chicks. Hunting and egg-collecting by humans have been implicated as a factor in the decline of South American wood storks. Humans also cause nest failures through ecotourism. 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.

### Population number

According to Partners in Flight resource the total breeding population size of the Wood stork is 450,000 birds. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.

## Fun Facts for Kids

Probably because of its decurved bill, the Wood stork has formerly been called the "Wood ibis", although it is not an ibis. The bird also has been given the name of the "American wood stork", because it is found in the Americas. Its regional names include "flinthead", "stonehead", "ironhead", "gourdhead", and "preacher".

The Wood stork is the only stork that breeds in North America.

Wood storks can travel over 80 kilometers (50 mi) to reach foraging sites using a wide variety of habitats.

- It is estimated that an adult Wood stork needs about 520 grams (1.15 lb) of food per day to sustain itself. For a whole family, it is estimated that about 200 kilograms (440 lb) are needed per breeding season.

The legs of Wood storks often appear white; this happens because birds defecate on their legs to provide cool. In hot weather, parents also shade their chicks with their wings.

Wood storks without a nest sometimes 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.