American White Ibis - Distribution and Habitat

Distribution and Habitat

The American White Ibis is most common in Florida, where over 30,000 have been counted in a single breeding colony. It also occurs throughout the Caribbean, on both coasts of Mexico (from Baja California southwards) and Central America, and as far south as Columbia and Venezuela. The non-breeding range extends further inland, reaching north to Virginia, and west to eastern Texas.

The species is known to wander, and has been sighted, sometimes in small flocks, in states far out of its usual range.

In North America, breeding takes place along the Atlantic coast, from the Carolinas south to Florida and thence west along the Gulf Coast. Laguna Cuyutlán is an isolated and regionally important wetland in the state of Colima on México's west coast where a breeding colony has been recorded. American White Ibises are not faithful to the sites where they breed, and large breeding colonies composed of ten thousand birds or more can congregate and disband in one or two breeding seasons. Breeding populations across its range have fluctuated greatly with wholesale movement between states. Until the 1940s, the species only bred in large numbers in Florida, mostly within the Everglades. Drought conditions elsewhere in the United States led to over 400,000 American White Ibis breeding there in the 1930s. In the 1950s and 1960s, large colonies appeared in Alabama, Louisiana, and then North and South Carolina and the Gulf Coast of Florida, and finally Texas in the 1970s. Then, between the 1970s and early 1990s, breeding colonies declined and disappeared in South Carolina and Florida, and greatly increased in Louisiana, and North Carolina. Colonies last between one and seventeen years, their longevity related to size and quality of nearby wetlands. The longest-lasting are associated with wetlands over 800 km2 (300 mi2) in size. Degradation of wetland or breeding sites are reasons for abandonment. The population of American White Ibises in a colony at Pumpkinseed Island in Georgetown County, South Carolina dropped from 10,000 to zero between 1989 and 1990 as Hurricane Hugo had inundated nearby freshwater foraging areas with salt water.

The American White Ibis is found in a variety of habitats, although shallow coastal marshes, wetlands and mangrove swamps are preferred. It is also commonly found in muddy pools, on mudflats and even wet lawns. Populations that are away from the coast and shoreline, particularly in southern Florida, often reside in other forms of wetlands such as marshes, ponds and flooded fields. In summer, these move to more coastal and estuarine habitats as inland waterways become flooded with summer rains and the ibis find the water levels too deep to forage effectively.