Wading bird foraging ecology in a disturbed mangrove estuary in northwest Ecuador : commercial shrimp ponds vs. natural mangrove mudflats

Abstract

I compared wading bird foraging ecology in commercial shrimp ponds and natural mangrove mudflats in the Muisne River Estuary in northwest Ecuador. I estimated foraging habitat suitability by observing the foraging efficiency, diet, and behavior of great (Ardea alba) and snowy (Egretta thula) egrets, censusing birds, and measuring prey availability (i.e. prey density, standing crop, water depth, and diversity). Great egrets had greater foraging efficiency in shrimp ponds, while snowy egret foraging efficiency was greater on mudflats. Over 85% of prey items in snowy egret boluses were from shrimp ponds. Mean density, standing crop, length, and mass of prey items was significantly greater in shrimp ponds, but availability was limited by water depth and diversity. Great and snowy egrets utilized shrimp ponds as their primary foraging grounds, while all other diurnal wading bird species foraged primarily on mudflats, where the diversity of wading birds and their prey was greatest.