Location, mean bill length, mean δ15N and δ13C blood values, and habitat type for each sampling site.

Sample sizes are in parentheses. Habitat types of each site are general classifications of the locations in which birds were observed and captured.*Sample sizes are the same as for δ15N values.Freshwater marsh = no contribution of brackish or salt water from marine sources.Lagoon = a shallow body of salt or brackish water where tidal turnover is low.Salt ponds = artificial salt evaporation ponds.Saltmarsh = vegetated marsh regularly flooded by salt or brackish water.Marine-tidal = expansive tidal mudflats inundated daily.