Systematics

Species originally described by Linnaeus in 1758 as Platalea Ajaia. This formal description was based chiefly on depiction of a bird from e. Brazil (type locality later designated as São Francisco River) called Aiaia Brasiliensibus by Georg Marcgrave in 1648 (Am. Ornithol. Union 1998). Monotypic genus Ajaia first used for Roseate Spoonbill by H. G. L. Reichenbach in 1853.

No geographic variation reported; no subspecies recognized or proposed.

All species of spoonbills sometimes placed in genus Platalea (Amadon and Woolfenden 1952, Sibley 1960, Steinbacher 1979, Hancock et al. 1992). Roseate Spoonbill maintained in monotypic genus Ajaia by Am. Ornithol. Union (1998); simple trachea and distinctive plumage used, in part, to justify this classification (Hancock et al. 1992).

Relationships among spoonbills poorly known. Roseate Spoonbill thought not closely related to most Old World taxa, including Eurasian (Platalea leucorodia), Royal (P. regia), Black-faced (P. minor), and African (P. alba) spoonbills (Hancock et al. 1992). Both Roseate and Yellow-billed (P. flavipes) spoonbills of Australia sometimes placed in separate monospecific genera apart from other spoonbills—Yellow-billed in Platibis and Roseate in Ajaia (as noted above); these 2 species may be more closely related to each other than to Old World taxa listed above (Hancock et al. 1992). Shared similarities that set these 2 species apart from other spoonbills include lack of nuchal crest, presence of spiky neck-ruff, and possibly simple (noncoiled) trachea (Allen 1942, Amadon and Woolfenden 1952, Vestjens 1975b).

Spoonbills are closely related to ibises, with more similarities than their differing bill morphology suggests; each placed in separate subfamilies—Threskiornithinae for ibises and Plataleinae for spoonbills (reviewed in Hancock et al. 1992). Evidence used to classify ibises and spoonbills in a single family, Threskiornithidae, is based on shared morphological features, DNA hybridization data, and comparison of egg-white proteins (Sibley 1960, Hancock et al. 1992). Hybridization between a spoonbill and an ibis is known: Black-faced Spoonbill × Black-headed (or Oriental White) Ibis (Threskiornis melanocephalus; Hancock et al. 1992).