 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 ( 310 sq mi ) 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 . 
