Interesting Facts About Wood Storks

Wood storks are rather easy to see near wetlands in the southern United States. Thought, their natural history, and behavior are rather peculiar. Here are some facts about the wood stork that you may find interesting.

These two young wood storks are about two weeks from leaving their nest. Photo: US Fish & Wildlife Service.

The wood stork is usually among the largest wading bird throughout its range

Wood storks are among the largest wading birds within their range. In North America, it is only second to the great blue heron, which is bigger in almost every measure.

Roseate spoonbills (Ajaia ajaja) are large wading birds, but their measurements are smaller.

The sandhill (Antigone canadensis) and whooping (Grus americana)  cranes are not considered wading birds as they do not actively wade in the water for the purpose of feeding.

In most of South America, the wood stork takes third place after the massive jabiru stork (Jabiru mycteria) and the larger and similar in appearance maguari stork (Ciconia maguari). 

Adult wood storks give their chicks cooling showers in the nest

Wood storks bring water into their crops to regurgitate/shower their chicks in the nest during the day’s hot hours.

Both parents regurgitate water over the chicks to cool them off. As the parents shower the chicks, they drink water and preen themselves.

Often the regurgitation behavior is accompanied by one of the parents extending one or two wings to block the sun and create shade for the young chicks.

Other stork species appear to exhibit the same behavior since their nests are exposed to the elements without any overhead cover.

The wood stork is a tropical bird 

Wood storks are found in tropical America, from Mexico to Argentina, between latitudes 35 north and south.

The southern United States is the northernmost part of the wood stork’s range.

Traditionally, wood storks nested in the Florida peninsula south of Lake Okeechobee. They began expanding their breeding range northward in the mid-1970s and early 1980s.

Specifically, in 1976, 16 pairs nested in the State of Georgia for the first time. By 1995, nesting pairs in the state grew to approximately 1,501 pairs.

Later in 1981, 11 wood stork pairs nested in North Carolina. By 1995 approximately 829 pairs nested in the state. (U.S. Fish and Wildlife Service 1996)

Although causes for such population expansion are poorly understood, climate change may be playing a role.

Wood storks have the fastest known reflex action in the animal world

In order to catch their prey, wood storks submerge their beaks into the water, setting up a trap in a sense. With their beaks open and submerged, storks either stand still while they startle prey with their feet or walk while moving their beaks from side to side.

When a scaping fish touches a wood stork’s beak or even creates turbulence between the open beak, the stork snap-shuts its beak trapping the prey.

According to experimental studies, the wood stork reflex action is the fastest known in the animal kingdom.

Data from experimental studies indicate that a wood stork snap-shut its bill at a speed of 0.25 milliseconds. This is to say that a second is divided into 1000 equal parts; the wood stork takes only the first 25 parts. This is fast!

To put this in perspective, it takes between 100 and 400 milliseconds for a human to blink an eye. Wood storks snap shut their beak in a fraction of the time it takes a human to blink an eye.

The studies also concluded that the wood stork’s snap-shut speed is twice as fast as the escape reaction of its prey. 

Young wood storks lose their voice and become almost mute as adults

Nestling wood storks are vociferous and loud. They give different call types when they interact among themselves and when they beg for food from their parents.

Adult wood storks are practically mute. They can give soft hissing noises and grunts during interactions. They can also make clattering or snapping noises with their beak.

Once the young wood storks leave their nest, they progressively lose their voice. Probably because they no longer need to communicate with their parents about the need to be fed. 

By the end of the first year after leaving the nest, wood storks have lost their ability to vocalize and can only make the soft noises of the adults.

An alligator is often necessary for wood stork nesting colonies to become active

Wood storks breed in nesting colonies. An essential requirement for a colony site is that the base of the trees is flooded or surrounded by water.

Anecdotal observations suggest that wood stork will not use any site even when it meets the conditions of having a flooded base or the trees are surrounded by water. 

They need a guard, an alligator that ensures that land predators are less likely to swim across the water to reach the colony.

Pond islands created to attract nesting wading birds, including wood storks, were not used by the birds despite meeting the right conditions. Only after an alligator(s) was present in the pond triggered wading birds to use the island for breeding. 

Alligators are often attracted to wading bird colonies where they eat chicks that fall out of their nests.

How long do wood storks live?

Wood storks have long lifespans. They live for at least 22 years and four months. This lifespan was obtained from a bird banded in the State of Georgia on 6/3/1994 and later observed in the state of Florida on10/11/2016. This bird may still be alive. This information was obtained from “Longevity Records of North American Birds,” compiled by the U.S. Geological Survey’s Patuxent Wildlife Research Center in Maryland.

How many wood storks are there?

According to the “Partners in Flight Science Committee (2021)”, there are approximately 300,000 wood storks in the Americas. Approximately 30,000 to 35,000 individuals are found in North America. 

Most wood storks occur in Central and South America. 

Wood Stork’s function in the ecosystem

The wood stork is a top predator that influences the ecosystem’s structure and balance by controlling its prey’s abundance, distribution, and diversity.

Controlling the abundance and diversity of their prey has a cascading effect on the food chain. 

As such, the wood stork is an indicator of the ecosystem’s health in which it lives.

The wood stork is an indicator species for the Everglades restoration program in South Florida. Wood stork populations’ responses to habitat management indicate the success of restoration activities. 

Threats to wood storks

Heavy metal concentrations such as mercury, cadmium, and lead have always been a concern for fish-eating birds, including the wood stork.

A comparative study found that birds in South Florida had higher concentrations of heavy metals in their tissues than wood storks in Central America.

Heavy metals concentrations in wood storks were higher than those known to harm other bird species. However, their effects on wood storks are poorly understood.

Habitat loss and degradation

The wood stork lives in warm regions in North America, which are also among the most desired places to live. Wetland habitats are under intense pressure for conversion to residential and commercial development.

But the story of wood stork habitat degradation dates back to the massive habitat transformation of wetland habitats in the 1930s and 1960s. From an estimated 12,000 breeding pairs in South Florida in the 1960s, population numbers plummeted to 2500 pairs in 1978.

The estimated current population size in North America is about 12,000 pairs.

Collisions and electrocution

Wood storks forage in wetlands of any type, including those located near busy roads. Wood storks are frequently involved in collisions with moving vehicles as they fly low to the ground.

Utility wires are also a danger to wood storks. Collisions with wires often result in incapacitated birds rather than death.

Electrocution is not as prevalent as it is in raptor species. Wood storks seldom use utility posts and wires as perches.

Is the wood stork endangered? 

Wood storks are no longer endangered. In 1984, the United States Federal Government declared the wood stork to be endangered under the Endangered Species Act. Continual recovery and management strategies took 30 years to bring the population back to the established recovery goals.

The Federal Government downlisted the wood stork from threatened to endangered in June 2014 after conservation efforts met recovery goals.

Wood stork populations are presumably stable or growing. As a sign of their apparent population growth, wood storks are occupying areas that they did not use to occupy.

How does the law protect the wood stork?

In accordance with the Endangered Species Act of 1973, the wood stork is listed as being threatened with extinction in the United States.

Wood storks are also protected under the Migratory Bird Treaty Act, which covers all bird species in North America, including Canada and Mexico.