Figure 1.
Location and elevation map of study site.
(Note: apparent crenulations of the water edge on Broad and Semi-Enclosed Flats are artifacts of the elevation measurement technique.) Base layer photograph from Bing Maps Aerial Imagery.
Figure 2.
Sediment samples from all flats and all tidal heights were taken at low tide. The relative position of where the sediment samples would be taken subsequently is indicated by the darker crosses in each of the diagrams showing earlier tidal stages.
Figure 3.
Mean density and biomass of major benthic macrofaunal taxa by flat and tidal stage.
Bivalves are not shown because there was no significant difference in abundance among flats at any tidal stage, and only one significant difference in biomass (see Tables S7 and S8). Gastropod biomass includes shell mass.
Figure 4.
N-MDS ordinations displaying similarities/differences among shorebird and benthic community compositions and sediment grain-size distributions.
Results of (A) benthic community composition, (B) sediment grain-size distribution, and (C) shorebird community composition n-MDS ordinations, comparing each combination of flat and tidal stage, with overlays of circles and ovals grouping flats according to cluster analysis results. Similarities given in percent. Grain-size cluster analysis overlay (B) is based on dissimilarity; increasing “Distance” values indicate an increase in dissimilarity among samples. Stress value of 0.12 (A) indicates that the 2-dimensional n-MDS ordination is an adequate and useful representation of sample relationships; stress value of 0.02 (B) indicates that the 2-dimensional n-MDS ordination provides an excellent representation of sample relationships; stress value of 0.08 (C) indicates a good representation. In (B), symbols for Semi-Enclosed Flat at late ebb and low tides are superimposed. In (C), Shell Flat at late ebb tide is not depicted because birds were never observed on the flat at that tidal stage.
Table 1.
Results of shorebird community PERMANOVA analyses testing for significance of variation among tidal flats.
Figure 5.
Flat use by shorebird foraging guild.
Percentages are flat-specific. All tidal stages combined.
Table 2.
Results of one-way ANOVAs comparing mean shorebird densities among tidal flats, as a function of tidal stage.
Figure 6.
Mean foraging shorebird (A) abundances and (B) densities, by flat and tidal stage.
Shell Flat is plotted for comparison only; it was not included in statistical tests due to low sample size when fisherman disturbance dates were excluded. Asterisks indicate submerged flats.
Figure 7.
Trends in abundance of commonly observed shorebird species: by tidal stage.
All flats combined.
Table 3.
Predominant foraging modes of all observed shorebird species.