Migration

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

Figure 2. Annual cycle of the White Ibis

Nature Of Migration In The Species

A highly nomadic species undertaking postbreeding dispersals, migrations, prebreeding intraregional population shifts, and regular rainfall-initiated shifts between interior wetlands and coastal habitats (Kushlan 1976a, 1979a, 1981; Kushlan et al. 1985, Frederick et al. 1996, Melvin et al. 1999). In general, breeds along Gulf and south Atlantic coasts, inland and coastal sites in Florida, Cuba and coastal Central and South America. Winter range varies; usually southern portion of North American range, Gulf coast, Greater Antilles, coastal Central and South America (see Distribution). Links between specific breeding and non-breeding ranges are unknown. Postbreeding dispersals often take individuals outside normal nonbreeding range (Fig. 1). Birds, especially juveniles, occur north as far as New York and Vermont, through Midwest North America into Quebec, Illinois, Missouri, N. and S. Dakota, Wyoming, Colorado, s. California, also in some instances in the Bahamas, Caymans, Puerto Rico, Curaçao, and Trinidad (www.ebird.org).

Dispersing northern birds begin migration by drifting southward into Georgia, Florida, along Gulf of Mexico to Mexico, also to Cuba. In 1950s and 1960s numerous birds banded in S. Carolina as nestlings were recovered in Cuba. Wintering birds from North America may move as far as Central America, and one bird banded as a nestling in coastal S. Carolina was recovered in Colombia (Post et al. 1985, Melvin et al. 1999).

Timing And Routes Of Migration

Timing and routes remain unclear. Band returns suggest a general north – south migration corridor (Melvin et al. 1999). Large flocks of ibises move south through s. Florida in fall (Oct-Nov); species also winters along the Florida coast and inland wetlands (JH). Birds wintering in s. Florida tend to depart roosts for northern breeding areas mid-Mar through Apr (Frederick et al. 2001). Although departure for spring migration is protracted, S. Carolina birds return to breeding sites in large numbers over just a few days, suggesting birds linger along migration route until conditions permit more rapid dispersal into breeding areas.

Likely trans-Gulf/Caribbean migration: ibises banded in North America have been recovered in Cuba and Central and South America. Also large flocks of ibises regularly fly south from the Florida Keys (across the straits of Florida) in September and October (JH). More information needed on migration and wintering sites of specific population segments.

Control And Physiology Of Migration

No information.

Fossil History

Two indeterminate species of Eudocimus reported from Pliocene of N. Carolina and Florida (Wetmore 1956, Olson 1985). E. peruvians described from the Pleistocene of Peru (Campbell 1979), but differentiation from modern form is questioned (Olson 1981).