Marsh terraces in coastal Louisiana increase marsh edge and densities of Waterbirds

Abstract

We evaluated the influence of marsh terracing on waterbirds in Louisiana's Chenier Plain. Terracing is a novel technique used to slow coastal marsh loss. Terracing increases marsh edge and is assumed to slow erosion, decrease pond depth, and encourage vegetation production. From April to September 2005, we monitored waterbirds in paired terraced and unterraced ponds in three sites dominated by Spartina patens. We additionally sampled submerged aquatic vegetation (SAV) biomass, nekton density, and water quality. Waterbird density and species richness were 3.8 and 1.4 times greater, respectively, in terraced ponds. By foraging guild, probers, aerial foragers, and dabbling foragers were more abundant in terraced ponds. Waders were frequently more abundant in terraced ponds. Diver density did not differ significantly between pond types. Terracing increased marsh edge in ponds 3.5 times. Nekton and SAV were more abundant in edge habitat than in open water, but water quality, water depth, SAV, and nekton did not differ significantly between pond types and did not influence bird density. Bird densities were higher in ponds with greater proportions of marsh edge, possibly because they are morphologically constrained to forage in shallow water or because of abundant food near edges. © Society of Wetland Scientists 2009.