This is the most widespread ibis species, breeding in scattered sites in warm regions of Europe, Asia, Africa, Australia, and the Atlantic and Caribbean regions of the Americas. It is thought to have originated in the Old World and spread naturally from Africa to northern South America in the 19th century, from where it spread to North America. The Glossy Ibis was first found in the New World in 1817 (New Jersey). Audubon saw the species just once in Florida in 1832. It expanded its range substantially northwards in the 1940s and to the west in the 1980s. This species is migratory; most European birds winter in Africa, and in North America birds from north of the Carolinas winter farther south. Though generally suspected to be a migratory species in India, the glossy ibis is resident in western India.
The Great Egret is generally a very successful species with a large and expanding range, occurring worldwide in temperate and tropical habitats. It is ubiquitous across the Sun Belt of the United States and in the Neotropics. In North America, large numbers of great egrets were killed around the end of the 19th century so that their plumes could be used to decorate hats. Numbers have since recovered as a result of conservation measures. Its range has expanded as far north as southern Canada. However, in some parts of the southern United States, its numbers have declined due to habitat loss, particularly wetland degradation through drainage, grazing, clearing, burning, increased salinity, groundwater extraction and invasion by exotic plants. Nevertheless, the species adapts well to human habitation and can be readily seen near wetlands and bodies of water in urban and suburban areas.