A Comparison Of Shorebird Habitat Use Between Living Shorelines And Natural Fringing Marshes

We examined the use of fringing marshes by herons and shorebirds in the southern portion of Chesapeake Bay. From 13 pairs of natural fringing marshes and nearby, constructed living shoreline marshes, we completed analysis of videos recorded at discrete, 30-minute intervals (dawn, dusk, high tide, low tide) throughout the 2018 and 2019 field seasons (May through August). A total of 684 hours of recording yielded 91 individual observations of birds comprising six species. Spotted Sandpipers (Actitis macularius) were observed most frequently (25), but only at living shoreline marshes. Likewise, 15 of 16 observations of Green Herons (Butorides virescens) were at living shoreline marshes. Great Blue Herons (Ardea Herodias; 19), Great Egrets (Ardea alba; 16), and Yellow-crowned Night Herons (Nyctanassa violacea; 14) were observed at both living shoreline and natural fringing marshes, and a single Willet (Tringa semipalmata) was observed at a living shoreline marsh. Bird species richness was significantly higher at living shoreline marshes relative to natural fringing marshes (2.2 ± 0.26 vs 1.0 ± 0.20, respectively; Wilcoxon signed-rank test, V = 45, p = 0.008). Spotted Sandpipers spent significantly more time on average at living shoreline marshes relative to natural fringing marshes (514 s vs 0 s, respectively; V = 36, p = 0.008), as did Green Herons (341 s vs 4 s; V = 36, p = 0.008). We found, however, no difference in time spent between marsh types for Great Blue Herons, Great Egrets or Yellow-crowned Night Herons. From generalized linear modeling, no models that included time of day, time since high tide, year, or marsh type fit the observational data better than the null model for any species. For Spotted Sandpipers, the model including Julian day yielded a better fit with a positive slope, indicating increased use of living shoreline marshes later in the season of observation. The rocky sills placed in front of constructed living shoreline marshes appear to provide refuge and/or foraging habitat for both Spotted Sandpipers and Green Herons. Because use of living shoreline marshes by other heron and egret species was similar to natural fringing marshes, we conclude that living shorelines as coastal management features provide habitat support for herons and shorebirds at least as well as natural fringing marshes