although scaup seldom occur in significant numbers. The increased tidal range 

 in this region results in very extensive flats that provide thousands of acres 

 of feeding grounds for black ducks. Presumably, invertebrate foods are 

 abundant and black duck populations utilizing the Machias and Cobscook Bay 

 units have not declined recently as have populations farther southwest. No 

 extensive eelgrass beds have been observed during low altitude flights over 

 the area at low tide. Generally the intertidal flat habitat is heavily 

 utilized by black ducks irrespective of ice conditions. 



Wintering eiders are not commonly observed east of Beals Island. The most 

 recent 5-year average count for eiders in the Machias Bay unit (table 15-5) 

 was only 32, and none for Cobscook Bay. 



The coast from Cutler Harbor to Lubec is bold, rock-bound, and, for Maine, 

 fairly regular. Waterfowl are not numerous along this stretch. In contrast, 

 the vast tidal flat between West Quoddy Head and Lubec, in additon to being a 

 general feeding area for many species of waterfowl and shorebirds, is one of 

 the few important stopovers for migrating brant. More than 5000 have been 

 estimated at times during the spring migration (personal communication from M. 

 A. Redmond, Lubec, Maine; February, 1979). From West Quoddy Head upriver, 

 throughout Cobscook Bay and northward to Calais, tides may reach or exceed 20 

 feet (6 m; 22.8 ft., or 7 m, at Calais). Within this area, the Cobscook Bay 

 complex of inlets, tidal creeks, and rivers, plus strong tidal flows and rich 

 invertebrate fauna, create many acres of excellent wintering and migration 

 habitat for waterfowl. Scoters and old squaws frequent the deeper areas and 

 mussel bars, and goldeneyes, buffleheads, and black ducks utilize the 

 shallower areas and intertidal flats. Cobscook Bay has not experienced the 

 recent decline in wintering black duck numbers. Because of the strong tidal 

 flow, winter ice conditions are seldom as severe in region 6 as in regions 1 

 to 5. 



Although waterfowl density in inland waters is not as high in region 6 as it 

 is farther southwest, it is still high particulary for ring-necked ducks. The 

 low density human populations and lack of human development compared to the 

 rest of the coast, contribute further to the region's value as a natural area. 



Ecological Interactions 



Many ecological interactions take place among waterfowl, especially those 

 related to food and feeding habits. Breeding waterfowl, especially pre- and 

 post-nesting females and young up to about 6 weeks of age, tend to feed 

 heavily on invertebrate foods. The tendency towards eating plant food is 

 strongest in late summer and fall. This is notably true for the black duck, 

 wood duck, and blue-winged teal (Drobney 1977; and Swanson et al. 1977). What 

 effect feeding waterfowl may have on the abundance and distribution of 

 invertebrates (bottom dwelling forms) or on aquatic vegetation in Maine is not 

 known, but any changes are likely to be highly localized. An example is the 

 eider duck which sometimes depletes cultured oyster beds in the central 

 coastal area (personal communication from G. G. Donovan, Maine Department of 

 Inland Fisheries and Wildlife, Augusta, ME.; August, 1977). Blue mussels 

 sometimes are eaten in abundance by eiders and scoters. 



A high abundance of toxin-producing dinof lagellates ( Gonyaulus excavata ) , red 

 tide organism, and their assimilation and accumulation in the fleshy tissues 



15-34 



