Sea Duck Ecology - Conclusions

Both study areas appear to be important to long-tailed ducks and surf scoters, but for potentially different reasons. Data from this study suggest that the lower Chesapeake Bay and Atlantic coastal bays are important to long-tailed ducks throughout the winter. Similarly, surf scoters used the lower Chesapeake Bay site throughout the winter. In contrast, surf scoters appear to use the coastal bays as a staging area for subsequent regional movements or further southward migration; though this does not necessarily diminish the importance of these habitats to them.

Diets documented in this study show similarities and contrasts to those of sea ducks in the upper Chesapeake Bay. This is to be expected since salinity and benthic prey resources exhibit similarities and difference across the regions. Perry et al. (2004) suggest that sea ducks in the upper Bay use degraded oyster and gravel beds. We found some evidence of that in the lower Bay as well, but only minor use of healthy intertidal oyster reefs in Hog Island Bay. However, the overall density of potential prey was much higher in this coastal bay than in Chesapeake Bay. This may suggest that in areas of very productive benthic communities, the importance of epifaunal oyster bed communities diminishes. If this is indeed the case, then the inverse may be inferred; as benthic (especially infaunal) communities diminish in eutrophied estuaries such as Chesapeake Bay, hard substrate communities may become relatively more important to sea ducks.
There appears to be segregation between these two sea duck species across many levels. We documented subtle, but possibly important, temporal and spatial differences. It appears that long-tailed ducks and surf scoters exploit different dietary resources with the region, albeit with some overlap.
Several aspects of sea-duck conservation are suggested by our data. Both the lower Chesapeake Bay and seaward coastal lagoons are important to both long-tailed ducks and surf scoters, but species-specific habitat needs are at least partially different in both time and space. This suggests individual management perspectives for each species (e.g., protecting infaunal benthos vs. mobile crustaceans). Spatial analyses of prey availability, duck foraging sites, and diet composition can be used to better understand foraging ecology and inform conservation strategies. For example, spatially explicit plots of the relative diet proportion of individual ducks can suggest management options tied directly to anthropogenic activities such as hunting pressure, commercial fishing, and aquaculture development.
This study implies that the relationships between sea ducks and soft- and hard-bottom habitats in the mid-Atlantic are complex. In the face of continued habitat degradation and shoreline development, this type of detailed habitat data will be very meaningful and have practical impacts on sea duck conservation.

Reference

Perry, M.C., E.J.R. Lohnes, A.M. Wells, P.C. Osenton, and D.M. Kidwell. 2004. Atlantic Seaduck Project, USGS Patuxent Wildlife Research Center, Laurel, MD.
http://www.pwrc.usgs.gov/resshow/perry/scoters/default.htm.