to be adversely affected by loss of habitat and changes in food availability 

 due to tidal barrages include shorebirds (particularly semipalmated 

 sandpipers, semipalmated plovers, and black-bellied plovers), Bonaparte's 

 gulls, herring and black-backed gulls, and great blue herons. Altered tidal 

 flow and regimes that cause changes in such factors as salinity, turbidity, 

 temperature, and nutrient content interact to affect invertebrate communities. 

 This, in turn, affects their avian predators. 



Species feeding in or among tidal rips, tidal convergences, and tidally- 

 related upwellings might be adversely affected if these oceanographic features 

 are altered. One of the largest inshore tidal rips and upwelling areas in the 

 eastern U.S. occurs in waters off Eastport, Maine (region 6). Tides ebbing 

 from Cobscook Bay converge with waters draining Passamaquoddy Bay to form rips 

 and convergence lines. High tidal ranges and local bottom topography 

 contribute to the dynamics of this system. This area is a major feeding area 

 for northern phalaropes, Bonaparte's gulls, herring and black-backed gulls 

 (10,000 to 50,000), kittiwakes, and dovekies. Altering the timing of water 

 draining either bay may affect the position, extent, and duration of the tidal 

 rips, which may sharply reduce the abundance of food on which these birds 

 feed. 



Tidal amplitude outside the enclosed area also is likely to increase, which 



may affect the amount and quality of intertidal feeding areas. Estuarine 



emergent wetlands (salt marshes) are likely to be adversely affected by 



altered tidal amplitude, but intertidal mud flats might increase offsetting 

 losses inside the barrage. 



Environmental Contamination 



Several types of environmental pollutants may adversely affect survival and 

 reproduction of waterbirds. These include oil, pesticides and other toxic 

 chemicals, heavy metals, and industrial and domestic wastes. Several 

 excellent reviews of the effects of environmental contamination on waterbirds 

 (including waterfowl) have been published in technical journals. Much of this 

 section was summarized from the review papers of Ohlendorf and coworkers 

 (1978a), Howe and coworkers (1978), Farrington (1977), Lincer (1977), and 

 Albers (1977 and 1978). 



Oil . Contamination of marine and estuarine systems by oil poses a serious 

 threat to waterbirds along the Maine coast. Oil enters coastal waters by 

 spillage during transfer operations, discharges from refineries, regular 

 discharges from inhabited areas (street runoff, sewage discharge, and 

 boating), and by catastrophic spills. The extent of oil contamination in 

 Maine is discussed in chapter 3, "Human Impacts on the Ecosystem." Casco Bay 

 (region 1) and Penobscot Bay (region 4) have the largest numbers of oil spills 

 in Maine. 



The most serious effect of oil spills on waterbirds is feather oiling. Oil 



disrupts the structure of feathers, destroying their insulating properties and 



buoyancy. Moderately or heavily oiled birds drown or die of exposure. The 

 latter is potentially serious in the cold waters along the Maine coast. 



A number of oil or petroleum products are toxic to birds. Birds ingest oil 

 while preening oil-coated feathers, drinking, or eating oil-covered food, and 



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