Effects of Landscape Heterogeneity across Intertidal Sandflats on Charadrii Bird Communities: The Influence of Man-Made Oyster Reefs
Creators: name: Rankin, Rachael
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2020

description: Widespread degradation and loss of oyster reef habitat has resulted in restoration projects as a means of regaining ecosystem services pertinent to estuarine ecology. Construction of man-made reefs through these projects often occurs upon intertidal sandflats due to their general capacity to meet conditional constraints of oysters as well as lack of significant structural complexity that would prevent such projects from occurring. In order to determine consequences of reef restoration projects for the populations that rely upon intertidal sandflat habitat, this study investigated whether alteration of habitat heterogeneity through reef construction caused significant shifts in the composition and behavior of wading bird (Charadrii) communities. This research occurred in estuaries near Beaufort, N.C., specifically at two sites located in Middle Marsh and Newport River. Each site contained subsites belonging to one of two treatment types: intertidal sandflats with and without man-made oyster reefs. Bird abundance upon each subsite was observed both in the field and through video footage analysis. 
Comparison of wading bird communities relative to treatment type evidences differences in both bird abundance and species composition, as fewer species and birds per acre were observed on average upon intertidal flats with man-made reefs than intertidal flats without man-made reefs. This determination is substantiated by the results of video footage analysis. However, the frequency at which birds were observed performing resting and feeding activities did not differ substantially between treatments, suggesting that the presence of reefs does not significantly alter the capacity for wading birds to use intertidal sandflats for these activities. Intraspecific analysis revealed lower abundances of sanderlings, dunlins, semipalmated sandpipers, black-bellied plovers, herring gulls, laughing gulls, ring-billed gulls, Forster’s terns, and dowitchers upon intertidal flats with reefs than upon those without reefs. Of these species, sanderlings, short-billed dowitchers, and semipalmated sandpipers are considered at-risk, such that reef restoration projects may contribute to their decline by decreasing the availability of useful or preferred habitat. However, three species were evidenced to benefit from reef restoration, American oystercatchers, willets, and ruddy turnstones, through observation of higher abundances upon subsites with reefs than those without reefs. Furthermore, the American oystercatcher and ruddy turnstone are also both at-risk species, such that reef restoration projects may be reintroducing valuable habitat that could help preserve or even bolster their populations. Consequently, abundances of the five at-risk species should be closely monitored in order to assess the extent to which reef restoration projects harm or benefit each species. 
Investigation into weather parameters, specifically water level and wind speed, as proxies of site conditions suggests that the observed discrepancies between treatment types should largely be attributed to differences in habitat heterogeneity between treatment types rather than variation in these parameters themselves. In general, data indicates that restored reefs influence the composition and abundance of wading birds species upon intertidal sandflats, but not all species are affected to the same extent. Further investigation is needed relative to the fitness consequences of reef presence as well as the influence of seasonality upon results, for bird community composition shifts throughout the year due to migratory behaviors, as well as in response to tidal cycles and other cyclical weather events.