Introduction

Juvenile White Ibis, Hatteras, NC, 15 October 2005

Adult breeding White Ibis

Figure 1. Normal breeding and nonbreeding range of the White Ibis.

The White Ibis is a striking, white wading bird with a long, distinctively decurved bill. It usually nests, feeds, and flies in large conspecific flocks, and in many ways epitomizes the freshwater and coastal wetlands of the southeastern United States. Historically one of the most abundant of North American wading birds, it still maintains large regional populations with a few nesting colonies of 20,000–30,000 pairs.

This is a bird of freshwater and estuarine wetlands—typically cypress swamps, bottomland hardwood and mangrove swamps, as well as freshwater marshes and salt marshes. Ibises are known for frequent shifts in roost and colony sites (Bildstein et al. 1990, Gawlik et al. 1998), substantial dispersal and migration distances (Frederick et al. 1996, Melvin et al. 1999) and variable breeding seasons (Heath 2002, Piazza and Wright 2004, Frederick et al. 2006). Nomadic movements and flexible reproductive schedules allow ibises to exploit the changing availability of shallow water feeding sites and concentration of its main prey, crustaceans and small fishes (Kushlan 1979a, Gawlik 2002). Because of salt stress, nestlings do not develop normally on brackish water crustaceans, so nearby freshwater feeding sites are essential for successful breeding at coastal colonies (Johnston and Bildstein 1990).

The dependence of White Ibis on favorable feeding conditions in wetlands, the conspicuous nature of their large flocks and colonies, and their eye-catching appearance has made the species a symbol for wetland conservation and restoration, especially in Florida where ibis habitat is threatened by development, pollution, and water management. Numerous studies have investigated trends in White Ibis distribution, abundance and reproductive success (Crozier and Gawlik 2002, Crozier and Gawlik 2003b, Frederick and Ogden 2001, Frederick et al. 2001, Frederick and Ogden 2003, Stolen et al. 2005, Herring 2008), and/or ibis contaminant levels (Frederick et al. 2002, 2004, Heath and Frederick 2005, Rodgers 1997), and used this information to infer ecosystem health.

No subspecies are recognized, but the Scarlet Ibis (Eudocimus ruber) of South America is closely related and is considered by some to be a conspecific color morph.