A group of ibises is called a colony, a fitting term for wading birds that nest and breed in large, densely packed communal groups, often alongside herons, egrets, and spoonbills in mixed-species wetland rookeries. Ibises use their long, curved bills to probe soft mud for crustaceans, insects, and small aquatic creatures.
Ibis colonies can number in the thousands during breeding season, with nests packed closely together in trees or dense marsh vegetation. That density offers real safety benefits, more eyes watching for predators and less chance any single nest gets targeted, even though it also means fierce competition for the best nesting spots.
Bonus fact: the sacred ibis was revered in ancient Egypt and closely associated with Thoth, the god of wisdom and writing, and mummified ibises have been found by the millions in ancient Egyptian burial sites.
“Colony” is shared broadly across many colonial nesting birds, making it one of the more common terms across the wider wading-bird world.
Related: Collective Nouns for Birds · What Is a Group of Ibises Called?