Wood storks are wading birds.  They feed on small fish 1 to 6 inches long, primarily topminnows, sunfish and some shrimp in freshwater areas and mummichogs and killifish in coastal settings.  To capture prey, they use a specialized technique called grope-feeding or tacto-location.  In 6 to 10 inches of water, the stork probes under the surface with a partly open bill.  When it touches a fish, it snaps shut.  The average response time of this reflex has been measured at 25 milliseconds, making it the fastest reflex known in vertebrates.  Storks may also “flash” or suddenly extend a wing out away from the body to either startle a fish into movement or provide a shaded area that attracts fish.

Excellent fliers, wood storks use thermals to soar thousands of feet high and as far away as 80 miles from nesting to feeding areas.  They glide with legs and necks extended.  As they descend from high altitudes, storks may perform some amazing dives, rolls and turns.

Wood storks are highly colonial birds and require 100 to 120 days to complete the breeding season (beginning with courtship to departure of young from the breeding site).  All storks exhibit very elaborate courtship behavior.  Males usually arrive at the colony site first and establish territories where they will build a nest; these territories are defended from other males.  Individual females begin approaching the males, who usually chase them away from their nest site over a period that can last for hours or days, until the male finally accepts her, or she goes looking elsewhere.  Wood storks do not mate for life.  During this time, the colony is very noisy. 

Once paired, the duo builds a nest of sticks, vines, leaves, and Spanish moss that varies in diameter from 20 to 35 inches, as many as 2 to 20 nests may be found in a single tree.  Nesting takes place in large rookeries and feeding flocks.  Nesting periods vary geographically.  In south Florida eggs are laid as early as October; in central and north Florida, Georgia and South Carolina eggs are laid from March to late May.

Two to five eggs are laid one to two days apart.  Both parents share incubation duties.  Hatching occurs after 28 to 32 days in the order each egg was laid.  Each chick weighs approximately 2 ounces (60 grams).  They are helpless and unable to fly.  Competition for food is fierce, and if food is scarce, only the older chicks will survive.  Week-old chicks are fed about 15 times per day, and they grow rapidly.  By 14 days, each will weigh 10 times their hatching weight.  At 28 days, each is 25 times heavier.  Parents take turns guarding the nest from predators such as vultures, crows, and grackles, and flying to feeding grounds that may be up to 80 miles away.  During the breeding season, wood storks need over 400 lbs. of fish to feed themselves and their offspring.  When it is very warm, parents also collect water and bring it to the nest to drool on and into the mouths of the chicks.  By 4 weeks of age, both parents leave the nest to search for food, and this continues until the chicks “fledge” or leave the nest.  Young may continue to return to the colony for another 10 to 15 days to roost or to try and get food from their parents.  A colony is considered successful if its parents average at least 1.5 fledged young per nest.

Tacto-location feeding enables wood storks to feed as successfully at night and in muddy waters as during the day in clear waters.  Feeding in large groups has its advantages, too.  The more birds there are moving through the waters, the more active the fish will be and thus easier to locate and catch.

Soaring flight saves energy.  Less flapping means less energy expended traveling from one place to the next.

Like many other bird species, wood storks roost together in flocks when they are not involved in an activity such as feeding or nesting.  Some advantages to this behavior are: 1) ease of locating feeding sites; 2) increased protection from predators; and, 3) thermoregulation.

Historically, wood storks may have nested in all of the southeastern coastal states from South Carolina to Texas.

The wood stork was formerly known as the wood ibis.  The word wood was included in the name as reference to this species’ preference for perching and resting in trees.  And, when the bird’s mandibles (upper and lower bills) come together, it sounds like two pieces of wood striking each other.

The name stork has been in existence for thousands of years.  A Scandinavian legend tells us that when Christ was on the cross, the stork flew around crying, “styrket, styrket –“, which means “strengthen ye”.  The origin of the name is probably from the word stark, meaning strong, a description of the rigid posture of storks.

During the last century, prior to the 1970’s, all wood stork nesting occurred in Florida and primarily in south Florida.  But as the human population and agricultural use of this region grew in the latter part of the 1900’s, the demand on the region’s water supply forced changes on the natural hydrology.  First came the diking of Lake Okeechobee, the source of the Everglades water.  Ditching came next for mosquito control.  All this combined with land development, expanded agricultural use, and periodic droughts made it difficult for nesting wood storks to find enough fish to successfully fledge offspring.  In 1930, there were an estimated 60,000 wood storks (20,000 nesting pairs).  Today, there are approximately 9,000 (4,000 nesting pairs). 

The wood stork was listed as a federally endangered species in 1984 due to the severe drop in their population.  Under this protection, all wood storks and their required habitats are protected.  In addition, state laws in Alabama, Florida, Georgia, and South Carolina also protect this species.

The breeding season is synchronized with the wetland cycles.  If there is too much rain and water levels are too high or there is a drought and water levels are too low, storks will not be able to catch enough of the right size prey to feed themselves or their chicks.  Each pair in the colony needs at least 440 lbs. of fish to feed themselves and successfully fledge their chicks each nesting season.  At two fully protected nesting colonies in south Florida, Corkscrew Swamp and Everglades National Park, wood storks have experienced frequent nesting failures in recent years.  This is attributed to adverse water management practices.

For continued survival in the United States, currently occupied nesting, roosting, and foraging habitat must be protected from further loss or degradation.  A prerequisite for the recovery of this species is the restoration and enhancement of suitable habitat throughout the various habitat types.  Recovery efforts would be more effective if everyone had a better understanding of population biology, movement patterns, foraging ecology and behavior, the importance of roosting sites, and the possible impacts of contaminants.

What You Can Do: Everyone, through actions and concern, can help ensure the future of Florida’s wildlife:

1. Never disturb wood storks or other birds in a rookery, as they may abandon their nests;
2. Be considerate when observing wildlife.  Boats, dogs, and people hiking nearby can disrupt courtship, nesting, and feeding;
3. Join conservation groups and actively participate in group projects;
4. Let your local, state and federal representatives know that you support the protection and proper management of Florida’s environments.

Wood storks have never been part of the animal collection, but have always been naturally occurring visitors, attracted by the abundance of food, the artificially regulated water levels, and the availability of suitable nesting and roosting trees. 

History of rookery at the Jacksonville Zoo:

• In 1999, 7 pairs did not successfully fledge any chicks.
• In 2000, 12 pairs successfully fledged 19 chicks (1.58 nestlings per nest). 
• In 2001, 21 pairs successfully fledged 45 chicks (2.14 nestlings per nest). 
• In 2002, 40 pairs successfully fledged 111 chicks (2.78 nestlings per nest).
• In 2003, 77 pairs successfully fledged 191 chicks (2.48 nestlings per nest).
• In 2004, 74 pairs successfully fledged 208 chicks (2.81 nestlings per nest).
• In 2005, 82 pairs successfully fledged 219 chicks (2.67 nestlings per nest).
• Currently, the Zoo’s colony is the most important recently established rookery in Duval County.