Systematics

First described in 1776 by P. L. Statius-Müller as Ardea tricolor . Placed in monotypic genus Hydranassa by Baird in 1858, a classification maintained by Bock (1956). Merged into genus Egretta following study of skeletal and behavioral characteristics (Payne and Risley 1976). The latter classification is generally followed at present (Hancock and Elliot 1978, Am. Ornithol. Union 1983, Sheldon 1987).

Specimens collected in Baja California are larger than those in e. U.S. (see Appendix 4), and races from ne. South America are smaller than other races (see below). No information on plumage variation within any races.

Three subspecies recognized on basis of size (see Appendix 4) and color of upperparts, chin, and median line of foreneck (Palmer 1962, Blake 1977, Payne 1979).

Gosse, 1847. From North America south to South America west of Orinoco River delta, and Caribbean north of Trinidad. Larger than the other 2 subspecies, slaty upperparts, white chin and foreneck. Included under ruficollis as a synonym is the name occidentalis (Huey 1927), ascribed to breeding populations in Baja California and northward wanderers in w. U.S., said to be larger, but this is disputed (see van Rossem in Grinnell 1928); occidentalis was recognized by Payne (1979).

(Hellmayr) 1906. Found only on Trinidad and possibly Tobago. Small; similar in size to nominate race (see below); neck and upperparts more blackish; chin and middle of throat dark chestnut; foreneck more or less strongly tinged rufous. This race synonymized under nominate tricolor by Payne (1979).

(Statius-Müller) 1776. Found east and south of Orinoco River delta on northeastern coast of South America. Smaller than ruficollis but similar in size to rufimentum; neck and upper surface of body lighter, more slaty gray; chin white instead of chestnut; median line of foreneck paler than that of rufimentum, closer to medium chestnut. Intergradation among the 3 races is suspected in zones of contact in n. South America (Bull 1985) and Caribbean (Wagenaar Hummelinck and Van der Steen 1977).

Based on behavior, skeletal, and muscular characteristics, probably closely related to Little Egret (Egretta garzetta), Snowy Egret (E. thula), Slaty Egret (E. vinaceigula), Eastern Reef Heron (E. sacra), and Little Blue Heron (E. caerulea; Sheldon 1987). Two cases reported of hybridization with Snowy Egrets (A. Sprunt in Dickerman and Parkes 1968, Meeks et al. 1996).