Colonies of Reddish Egret (Egretta rufescens) in Western Mexico

Abstract

Very little is known about the numbers and distribution of the Reddish Egret (Egretta rufescens) in western Mexico. To estimate the size and distribution of Reddish Egret colonies along the coast of western Mexico, historical and potential Reddish Egret nesting sites were surveyed in 2008 and 2009. Forty-six colonies were found from Baja California to Chiapas. Mean colony size was 24 pairs/colony (95% CI ± 15; n = 46), but most (74%) colonies were < 20 pairs (Median = 7 pairs; n = 46). The largest colony (258 pairs) and the only two colonies with dark and white morphs were found in Oaxaca. The second largest colony (248 pairs) was found in Baja California Sur. The total breeding population was estimated at 1,108 breeding pairs; 788 pairs in 43 colonies were located in northwestern Mexico (Baja California peninsula, Sonora and Sinaloa, subspecies E. r. dickeyi) and 320 pairs in three colonies were in southern Mexico (Oaxaca and Chiapas, subspecies undetermined). This breeding population, although small, is three to four times larger than previously reported for the Pacific Coast of Mexico (225-300 pairs). Thirty-five (76%) Reddish Egret nesting sites were inside a natural protected area; however, the Oaxaca and Chiapas colonies were not.