Wood Stork Nesting Habits 

The breeding biology of wood storks is fluid. Mated pairs last only a breeding season, and minor changes in the regional rain patterns can make or break the breeding outcome. This article looks at some aspects of the wood stork’s nesting habits.

  • Wood Stork breeding pairs last only one breeding season.
  • Pairs build a new nest each breeding season.
  • Breeding occurs between December and August in North America, depending on the region.
  • In South America (Brazil), they breed between June and October.
  • Wood storks lay two to five eggs.
  • Both parents incubate the eggs and take care of the chicks.
  • They breed only once a year
  • The breeding period lasts approximately 4 months
    Photo: US Fish & Wildlife Service.

In what months does the wood stork breed?

In North America, the wood stork breeds between the months of December through mid-August.

They initiate breeding activities according to the prevailing rainfall patterns, which may accelerate or delay the process.

In the southern United States (State of Florida), wood storks tend to breed between November through March. Further north in the State of Georgia, they breed between April through early August.

In South America, particularly in Brazil, the wood stork nests approximately between the months of June, July, August, September, and October.

Length of the breeding period

The reproductive period takes 120 to 130 days (approximately four months). The breeding season refers to the period between the time the female lays the first egg and the time the first nestling leaves the nest.

Since young wood storks leave the nest and return to be fed by their parents, it’s difficult to determine when the breeding period ends.

  • The wood stork in North America breeds between the months of December to August.
  • In South America (Brazil), they reproduce between the months of June to October.
  • The reproductive period lasts approximately 4 months.
  • The beginning of the breeding period varies regionally.

What triggers the wood stork breeding season?

Wood Storks use dropping water levels at their foraging sites as the most important signal for the start of the breeding season.

Fish populations grow exponentially in flood-prone areas during the rainy season due to the abundant water. Fish in large flooded areas are dispersed and difficult to catch.

As the dry season begins, the flooded areas begin to shrink to smaller and shallower ponds, where fish and other aquatic animals are concentrated and easier for the wood stork to catch. 

Nesting when water levels begin to recede ensures that plenty of food will be available once the chicks have hatched and are growing.

Timing does not always go according to plan

Wood storks build their nests on the assumption that food will be plentiful when the eggs hatch.

In some cases, this calculation doesn’t work out as expected, and continuous rain keeps large areas flooded when the eggs start hatching. High water and fish spread in large areas make catching enough food for the young birds very difficult.

If the variation in rainfall patterns is mild, fewer nestlings survive, but if it is significant, adults abandon the colony leaving chicks of all ages to starve to death.

How often do wood storks breed each year?

In North America, Wood Storks typically breed only once a year.

However, if a pair loses its eggs at the beginning of the incubation period, they will make another breeding attempt in the same season. 

If they lose their eggs late in the incubation period or lose their chicks, then they don’t attempt to breed until the next year. 

It is not known with certainty whether they breed more than once a year. However, there is one record of a tagged female having two successful clutches in one year.  

A double brood in a year may have to do with years of abundant food.

Little is known about the reproductive biology of the Wood Stork in Central and South America. 

Pair formation 

Males and females meet at the colony site, where they form a pair bond. When water levels begin to drop, wood storks congregate at their colonies.

Wood storks do not have elaborate courtship displays like those of other birds. They meet and form a pair bond quietly.

Adult birds meet at the colony site, forming pairs for the breeding season. Photo: US Fish & Wildlife Service.

  • Wood Storks form a new pair each year.
  • The males choose the nesting site.
  • The females inspect the colony and choose a male.
  • Two storks standing together at the nesting site indicate that a new pair has formed.
  • Courtship displays begin as early as October.
  • In North America, mating begins in November.

Field observations indicate that the male chooses the nest and may even begin to build the nest foundation. 

Females assess a male’s nest location within the colony. She shows interest by approaching the male standing at the nest site.

The male can be aggressive to the female at first. If he accepts her, she is allowed to stand and stays close to the potential nest site. When the two wood storks stand together, preening each other and copulating, a breeding pair has been formed. 

Do wood storks mate for life?

Wood Storks do not mate for life. They form pairs that last only one breeding season. 

Pairs break up at the end of the breeding season and do not appear to maintain close proximity after the breeding period is over. 

Each individual will find a new mate in the next breeding season. They may return to breed at the same colony or choose another one. 

It is unclear if birds that bred the year before and returned to the same colony breed together again. 

The nest of the wood stork

Wood stork breeding colony. Photo: South Florida Water Management District.

  • Each wood stork pair builds a new nest each breeding season.
  • They nest on the branches of living or dead trees but with the ground flooded to prevent predators from climbing up to the nest.
  • The male and female build a nest in two to three days.
  • The eggs are placed in the center of the nest, which has a small depression.
  • The nest measures 1 to 1.5 meters in diameter and is 18-25 cm high.

Wood Stork nests are large, and bulky, but flimsy. 

The bottom layer is made of thick and long branches. Additional layers are made of shorter and finer branches.  

The nest’s upper layer is made of finer material and has a central depression where the female lays her eggs.  

Adult birds defecate on the nest as they build it, often creating a semi-solid top layer composed of guano and nesting material.

Birds can steal nesting material from other nests within the colony given the opportunities. If a nest is abandoned, other birds building nests will concentrate on getting as much nesting material from the abandoned nest to build their own.

A wood stork nest is classified as a platform nest. A typical nest varies in diameter from 1 to 1.5 meters. The height also varies from approximately 18 to 25 cm. 

Nest Construction

A mated pair builds a nest in 2 to 3 days. Both parents actively work all day, often non-stop.

Males put almost twice as much effort into collecting nesting materials for further distances than females.

The female often remains in the nest, receiving the male’s material to accommodate it. But she also collects nesting material located at shorter distances.

Where do wood storks nest?

Wood stocks nest in colonies. Their nests are built on dead or live trees. Apparently, the type of tree is not very important. 

Wood storks build their nests at variable distances from the ground, depending on what is available. Studies of many nesting wood stork colonies indicate that nests are built between 2.6 to 27 mt from the ground.

The most important element is that the base of the trees where the colony is established is flooded or on dry ground but surrounded by water to prevent ground predators from accessing the colony.

One of the preferred tree species for nesting wood storks in North America is cypress (Taxodium spp), in which the nests are located high above the ground. Cypress trees typically grow in flooded areas.

When only mangroves are the only trees available, wood storks nest on mangroves. 

Do wood storks defend nesting territories? 

Wood Storks do not have breeding territories because they breed in colonies. The male chooses a spot within the colony to build a nest. 

A pair only defends its nest and the immediate surrounding area of the nest. This area can vary from 1 to 2 meters from the nest. 

Wood storks nest on top of the crown of trees. Spacing between nests is usually not a problem as suitable spots to build a nest naturally occur unevenly. 

Do wood storks use the same nest every year?

The wood stork does not reuse the same nest every year. Nests are dilapidated and soiled with excrement when the chicks leave the nest. 

Nests are usually blown down yearly, and wood storks using the same colony site have to build a new nest every year.  

Wood storks typically build a single nest per breeding season. Building two nests in a single season happens when a pair loses their eggs early in the nesting season. 

The second breeding attempt never happens on the same nest. Instead, the pair move to a different spot in the colony and builds a new nest to breed again. 

What are the nest predators of wood storks?

Climbing mammals such as raccoon (Procyon lotor) and, to a lesser extent, Virginia Opossum (Didelphis virginiana) are the most likely nest predators of the eggs and chicks. 

Crows can take eggs from unattended wood stork nests.

Egg laying and incubation

Typical nesting colony; an island surrounded by water. Photo: Ross Tsai.

  • The female lays one to five eggs.
  • She lays the entire clutch in about six days.
  • The female initiates incubation after laying the first egg.
  • The eggs are creamy white, with a finely grained surface.
  • The female and male incubate the eggs.
  • The incubation period lasts from 27 to 32 days.

Eggs of the wood stork

Wood Stork eggs are typically oval in shape and creamy white with a finely-grained surface. 

During incubation, the eggs become impregnated with guano and other bodily fluids from the parents and appear light brown and soiled.

There is no color variation among stork eggs.

Wood Stork eggs have very little variation.

Do the male and female incubate the eggs? 

Both storks share the incubation duties alternating shifts equally. 

Field observations suggest that the parents incubate the eggs continuously for a period of approximately 96 minutes before taking a break. During a break, a bird stands up and preens itself, or if it’s time, changes and shifts.

During the first week of incubation, the male and female stand close to the nest while one is incubating. 

The presence of both parents near the nest decreases as the incubation period progresses. At the time of hatching, only one of the parents is present.

Hatching and caring for the young

The first egg laid is incubated for a longer period of time and hatches first. Note the open eyes and the huge beak. Photo: US Army Corp of Engineers.

  • Not all the eggs hatch at the same time.
  • The chicks hatch with a thin layer of whitish down.
  • Both parents care for and feed the chicks at equal frequency.
  • For the first two weeks, the chicks eat food directly from the beak.
  • After the first 12 days, the parents begin to regurgitate food into the nest for the chicks to pick up and eat.
  • After leaving the nest, the chicks return to the nest for some time to continue receiving food from the parents.

The first egg laid and incubated is the first to hatch. Note the open eyes and the huge beak. Photo: US Army Corp of Engineers.

The wood stork chick first breaks the egg-shell, creating a bulge as in other birds. Then, it proceeds to break the shell through a lateral incision.

Wood stork biologists observed that a chick might take up to 7 hours to complete hatching. The parents discard the remains of the eggshell on one side of the nest.

Wood stork eggs hatch asynchronously, that is, at different times. This unequal time of hatching results from the fact that the female begins to incubate the first eggs and continues incubating as she continues laying eggs to complete the clutch.

The first egg laid has more days of incubation. Therefore, it hatches earlier than the last one. 

Hatching first gives the first chick an advantage as it receives food from the parents for one or two days, gaining a considerable size before the next egg hatches.

Baby wood storks

The chicks hatch with a fine layer of whitish down. The head is almost bald.

The beak is yellow/orange and thick at the base at the hatch, growing disproportionately fast in the subsequent weeks. A study that measured the beak’s growth found that it increased about 2.5 mm per day.

At the time of hatching, the beak is shorter than those of the adults, but it continues growing for the next few weeks.

Caring for the chicks in the nest

After hatching, both parents continue to take turns brooding the chicks to keep them at the right temperature.

This involves providing direct heat or standing and providing shade during the hours of intense heat by opening their wings to protect them from the direct sun

Intensive care lasts about a week, after which the chicks are only brooded at night.

Twenty days after hatching, the chicks are capable of self-regulating their own temperature, and the parents no longer brood them but remain next to the nest through the night.

Between 20 and 45 days, the parents begin to take longer and longer times away from the nest, only coming to feed the chicks sporadically.

The parents have to search for food for the ever-hungry chicks. Between 20 and 45 days of age, the chicks consume the largest amount of food and grow most rapidly.

When necessary, the parents provide shade for the chicks by spreading their wings over them at any age and when necessary. They also regurgitate water on the chicks as a way to cool them down, particularly during the hottest part of the day. 


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