Mycteria americana range from North America to Argentina. In the United States, wood storks nest in South Carolina, Georgia, and Florida. After breeding they may disperse north to North Carolina or west to Mississippi and Alabama.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Resident from southern Sonora, Mexican Plateau (rarely), U.S. Gulf Coast (Florida, formerly west to Texas), and Atlantic coast (South Carolina to southern Florida), south in lowlands to South America (to western Ecuador, eastern Peru, Bolivia, northern Argentina), and Antilles (Cuba, Hispaniola). The southeastern U.S. population is probably disjunct from those in Mexico-Central America. Some individuals, especially juveniles, wander north after the breeding season; may occur up the Mississippi Valley to Arkansas and west Tennessee and up the Atlantic coast to North Carolina; Mexican breeders may range to Texas and Louisiana. Recent breeding in the U.S. has occurred in Florida, southeastern Georgia (Ruckdeschel and Shoop 1989, Bratton and Hendricks 1990), and South Carolina. Center of breeding range in the U.S. has shifted northward since the mid-1970s (Ogden et al. 1987); the Everglades has become of lesser importance as a breeding area but remains critical as a foraging area, especially during dry years (Ehrlich et al. 1992), when possibly as much as 55% of the total U.S. population may use the Water Conservation Areas north of Everglades National Park (at least 8-10% in wet years) (Bancroft et al. 1992). Southeastern U.S. breeders winter within the breeding range, rarely north to northwestern Florida and coastal Georgia. In the U.S., the highest winter densities occur in peninsular Florida (Gulf and Atlantic coasts) (Root 1988).

Adults usually measure one meter tall and can have a wingspan of over one and a half meters. They have a blackish bill, accompanied with a scaly-looking, featherless head and neck which sticks out straight when flying. The majority of the birds' body is white except for the primary, secondary, and tail feathers which are black. Immature wood storks have a pale yellow bill and dull gray-colored head and neck.

Average length: 1 m.

Average wingspan: 1.5 m.

Average mass: 2500 g.

Length: 102 cm

Weight: 2702 grams

Differs from the jabiru by smaller size, smaller bill that turns downward rather than slightly upward, and by black (rather than white) flight feathers and tail. Differs from white ibis in larger size, thicker bill, and black tail. Differs from egrets and herons in having a curved bill rather than a straight one. (NGS 1983).

• Terrestrial
• Freshwater
• Marine

Wood storks inhabit mainly tidal waters, marshes, swamps, streams and mangroves. They hunt for prey in shallow, muddy-bottomed banks or wetlands. Their nests are ideally constructed in trees surrounded by water to limit depredation of the eggs.

Habitat Regions: temperate ; tropical ; terrestrial

Aquatic Biomes: brackish water

Wetlands: marsh ; swamp

Other Habitat Features: estuarine

Comments: Chiefly freshwater situations: marshes, swamps, lagoons, ponds, flooded fields; depressions in marshes are important during drought; also occurs in brackish wetlands. Nests mostly in upper parts of cypress trees, mangroves, or dead hardwoods over water or on islands along streams or adjacent to shallow lakes. Feeds in freshwater marshes, swamps, lagoons, ponds, flooded pastures and flooded ditches, depressions in marshes (especially during drought).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Individuals from Mexican west coast are regular post-breeding migrants in California and Arizona; breeders from eastern Mexico appear in Texas and Louisiana (Matthews and Moseley 1990).

Adult wood storks eat small fish, frogs, mollusks, snails, insects, and aquatic invertebrates. It has been calculated that a 2.5 kilogram bird would eat more than half a kilogram of fish daily. Wood storks wade through shallow water feeling for movement and snap their bill shut when they touch a fish. Vision is not as important as touch, and the bill-snapping reflex of the stork is one of the fastest reflexes known in vertebrates, taking only about 25 thousandths of a second (Wolkomir and Wolkomir, 2001). It was also recently discovered that wood storks often leave the roost at night to catch prey or fish during nocturnal low tides. This allows them to feed without the competition of other large shorebirds such as great egrets.

Animal Foods: amphibians; fish; insects; mollusks

Primary Diet: carnivore (Piscivore )

Comments: Eats mainly fishes (usually over 3.5 cm long), also miscellaneous other small animals, detected mainly by contact with touch-sensitive bill. Forages mainly in shallow water (about 15-50 cm deep) and flooded fields; attracted to areas with falling water level and hence concentrated food sources (Palmer 1962, Ogden et al. 1978). May feed cooperatively, wading together in shallow water (Hilty and Brown 1986). Conservative estimate is that one pair requires about 200 kg of fish in one breeding season to supply needs of adults and young (see Van Meter 1989). May travel long distances (sometimes over 100 km, usually not more than 56 km) between nesting and feeding areas when feeding young (Ogden et al. 1978).

Wood storks and other wading birds are an integral part of the marshland food chain along with other reptilian and mammalian predators.

The greatest threat to wood storks are raccoons (Procyon lotor) that climb to the nests to eat the chicks. Alligators (Alligator mississippiensis) may also pose a problem to unwary birds.

Known Predators:

• raccoons (Procyon lotor)
• American alligators (Alligator mississippiensis)

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 300

Comments: Occurs locally throughout range in North, Central, and South America.

10,000 - 1,000,000 individuals

Comments: There are no known rangewide estimates for population numbers. The largest colonies are in the Usumacinta-Grijalva delta in southeastern Mexico; these colonies had 5000-10,000 pairs in the 1980s (Ogden et al. 1989). U.S. breeding pupulation was more or less stable at 7000-10,000 pairs in the early 1990s (Bancroft et al. 1992). Manry (1993) stated that only 4086 pairs were found in U.S. range in 1991. The U.S. Fish and Wildlife Service (1996; see Federal Register, 25 March 1996, also) stated that the U.S. population was 5500-6500 pairs over the last 12 years. The Florida population was estimated at: 9400 adults in 1983; 9500 adults in 1984; 5215 pairs in 1985; and 5130 pairs in 1986. "Statewide surveys in 1993, 1994, and 1995 produced estimates of 4402 (29 colonies), 3588 (26 colonies), and 5523 (33 colonies), respectively, in Florida... The numbers of storks nesting [were]...1661 pairs at 11 colonies in Georgia (M. Harris, pers. comm), and 806 pairs at 3 colonies in South Carolina (T. Murphy, pers. comm.) during 1993." (Ogden 1996).

Notably gregarious. Roosts communally.

In Georgia, lower water level led to lower nesting success because of increased predation of young, presumably by alligators (Ruckdeschel and Shoop 1989). Rise in water level during nesting period may result in breeding colony abandonment (Ramo and Busto 1992).

Like other migrating birds, wood storks may locate their nesting grounds by recognizing geographical landmarks and sensing magnetic fields.

Perception Channels: magnetic

The eggs are incubated for one month and the newborn chicks hatch weighing only 57 grams. They are completely helpless except for the feathered umbrella that the parents provide with their wings to shield them from heat and rain (Klinkenberg 1998). There is sibling competition for food and under stressful conditions only the first-born and largest will survive. During times of heavy rains, nestlings often die or are deserted by their parents (Ramo and Busto 1992).

Wood storks are monogamous.

Mating System: monogamous

Pairs often mate for life and return to the same nest each breeding season to raise their offspring. Breeding occurs from December to April. Nests are constructed out of sticks high atop cypress, mangrove, or other trees in marshy woodlands. Wood storks nest colonially with from 5 to 25 nests in a single tree.

Females lay 2 to 4 (usually 3) eggs per clutch. Incubation lasts 28 to 32 days and the young fledge after 55 to 60 days. Woodstorks do not begin to breed until they are 4 years old.

Breeding season: December to April

Range eggs per season: 2 to 4.

Range time to hatching: 28 to 32 days.

Range fledging age: 55 to 60 days.

Average age at sexual or reproductive maturity (female): 4 years.

Average age at sexual or reproductive maturity (male): 4 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal )

Average eggs per season: 3.

Both the male and female take part in nest building, incubation and the feeding of their semi-altricial young. Chicks are fed regurgitated fish and are dependent on their parents for 55 to 60 days after they hatch.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female)

Nesting is tied to receding water levels and concentration of food sources, regardless of date. Clutch size is 2-5 (often 3). Incubation, by both sexes, lasts 28-32 days. Both parents tend young, which leave nest at 50-55 days (also reported as 9 weeks), return to nest for feeding and roosting until 75 days old. Nests in colonies of a few to thousands of pairs.

In Georgia, nesting was most successful if nesters did not experience (a) periods of cold weather and (b) raccoon predation that was associated with drying of the water under the colony (Coulter and Bryan 1995).

In the 1930's an estimated 20,000 wood stork pairs were nesting in the United States. In 1978 only 2,500 pairs were recorded and wood storks were placed on the Endangered Species List in 1984. A recent survey of nesting pairs counted 5,500 pairs (Klinkenberg, 1998). If the species grows to 6,000 nesting pairs it may be reclassified to "threatened" instead of "endangered". The best way to help the species is to preserve wetlands, limit water management, and reduce heavy metal pollution such as mercury which can be lethal to the storks (Bryan et al., 2001a).

Historically the largest American population of wood storks has been in Florida's Big Cypress National Preserve and the Everglades, but because of a decline in wetland habitat and water management, colonies seem to be migrating northward (Brooks, 2001).

Wood storks are listed as endangered on the US Federal List and are protected under the US MBTA.

US Migratory Bird Act: protected

US Federal List: endangered

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N3 - Vulnerable

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Large range from the southeastern U.S. and Mexico to South America; populations are relatively stable and apparently secure on a global basis; U.S. population has been stable in recent years, but nesting and feeding areas have been negatively impacted by human alteration of the natural hydrological conditions.

Global Short Term Trend: Relatively stable (=10% change)

Comments: The U.S. Fish and Wildlife Service (1990) categorized the status of the southeastern U.S. population as "stable." Breeding populations from Mexico to South America appear to be stable (Matthews and Moseley 1990).

Global Long Term Trend: Unknown

Comments: Rangewide trends unknown. Breeding population in the southeastern U.S. declined from 16,000-20,000 pairs in the 1930s to 10,000 pairs in 1960 to 2500-5000 pairs in the late 1970s (Ogden and Patty 1981, Spendelow and Patton 1988); increased to 5000-6000 pairs in the mid-1980s. Since the 1960s, the southern Florida population has substantially declined whereas populations in northern Florida, Georgia, and South Carolina have substantially increased (USFWS 1996).

Degree of Threat: AB

Comments: A major problem is low productivity, associated with inadequate food, caused in part by disruption and drainage of wetlands (see Van Meter 1989). The U.S. population (especially Florida) is threatened by human manipulation of water regimes, affecting both nesting sites and feeding areas. The long reproductive lifespan of the wood stork allows it to tolerate reproductive failure in some years, but artificially modified hydrological regimes, exacerbated by naturally occurring events (e.g., prolonged drought or unseasonal heavy rainfall), have caused nesting failures to become chronic in some of the important south Florida rookeries. Additional loss of habitat stems from logging and development. Nest predation by raccoons has been a problem in some areas. Human disturbance causes adults to leave their nests, exposing the eggs/young to predators (Van Meter 1989).

Restoration Potential: The earliest possible data for complete recovery of the U.S. population is 2005, but a more realistic date might be 2015-2020 (USFWS 1996).

Management Requirements: See recovery plan (USFWS 1996). Control of water level is critical to the management of this species. See Coulter (1990) and Matthews and Moseley (1990) for information on the successful creation of artificial foraging habitat at Kathwood Lake, Silverbluff Plantation Sanctuary, South Carolina.

Biological Research Needs: Continue research on the role of water management regimes in relation to productivity of rookeries. Study rookeries in north and central FL and the degree of interchange with south FL colonies. Monitor recruitment and factors that affect it. Evaluate dredge and fill activities for affects on wood stork nesting and feeding areas. Evaluate prey response to water management regimes.

Global Protection: Unknown whether any occurrences are appropriately protected and managed

Comments: Many occurences are in national wildlife refuges, national parks, National Audubon sanctuaries, and state-owned lands within the U.S. Unknown oustide U.S.; however, occurrences within protected areas can mean very little. Dramatic declines in the "protected" south Florida occurrences are thought to be the result of reduced nesting success, associated with an inadequate food supply caused in part by disruption and drainage of wetlands (see Threat Comments). See state ranking forms for specific protected sites.

Needs: Do whatever necessary to restore more natural hydrological conditions within the range of the wood stork. Provide adequate feeding habitat for existing rookeries. Restore and enhance habitat. Restrict the use of pesticides in stork habitat. Protect any nesting areas that are not yet protected. Increase public awareness. See recovery plan (USFWS 1996).

There are no known adverse affects of wood storks on humans.

We do not have information on economic importance for this species at this time.

Comments: Genetic analyses yielded no evidence of discrete subpopulations in Florida (Stangel et al. 1990). Indeed, Van Den Bussche et al. (1999) found low levels of genetic variablity among Georgia and Florida Wood Storks and recommended that "all colonies of Wood Storks in the southeastern United States be managed...as a single interbreeding population." Similar surveys of South and Central American populations are not available.