Trophic relationships of a marsh bird differ between gulf coast estuaries
Estuaries and Coasts
Egg, Fiddler crab, Mixing model, Northern Gulf of Mexico, Stable isotope analysis
Much of North America's tidal marsh habitat has been significantly altered by both natural and man-made processes. Thus, there is a need to understand the trophic ecology of organisms endemic to these ecosystems. We applied carbon (δ13C) and nitrogen (δ15N) stable isotope analysis, along with isotope mixing models, to egg yolk, liver, and muscle tissues of clapper rails (Rallus longirostris) and their likely prey items. This analysis enabled us to explore variation in trophic niche and diet composition in this important marsh bird in two northern Gulf of Mexico tidal marshes that are river and ocean-dominated. For the river-associated estuary, δ13C and δ15N of egg yolks, liver, and pectoral muscle tissue samples provided evidence that clapper rails maintained a similar diet during both the winter and the breeding season. A trophic link between C3 primary productivity and the clapper rail's diet was also indicated as the δ13C of clapper rail egg yolks related negatively with the aerial cover of C3 macrophytes. Clapper rails from the ocean-dominated estuary had a narrower trophic niche and appeared to be utilizing marine resources, particularly, based on modeling of liver stable isotope values. Variation in stable isotope values between egg yolk and liver/muscle in both systems suggests that endogenous resources are important for egg production in clapper rails. These results demonstrate that diet composition, prey source, and niche width of clapper rails can vary significantly across different estuaries and appear to be influenced by hydrological conditions. © 2010 Coastal and Estuarine Research Federation.
Rush, Scott A.; Olin, Jill A.; Fisk, Aaron T.; Woodrey, Mark S.; and Cooper, Robert J.. (2010). Trophic relationships of a marsh bird differ between gulf coast estuaries. Estuaries and Coasts, 33 (4), 963-970.