ish water and occur infrequently in salt water (Palmer 1976a) . In Chesapeake 

 Bay, these swans preferred open, extensive areas of brackish estuarine water no 

 more than 5 ft (1.5 m) deep (Stewart and Manning 1958, Stewart 1962). During 

 January, Whistling Swans used brackish estuarine bays 76% of the time, salt 

 estuarine bays 9%, fresh estuarine bays 8%, and slightly brackish estuarine 

 bays 6%. Other habitats (ca. 1%) used included coastal impoundments and fresh 

 and estuarine marshes. Fresh-water areas were used primarily by early fall ar- 

 rivals (Stewart 1962). 



FOOD AND FEEDING BEHAVIOR 



These swans normally dip their heads and necks into the water to feed on 

 bottom vegetation; when feeding in deeper waters they may tip up to seize sub- 

 merged foods (Bellrose 1976). In terrestrial situations Whistling Swans may 

 both grub and graze (Palmer 1976a) and may browse on shore grasses (Gilmer 

 1974). 



Food habits on the breeding grounds are largely unknown, but in migration 

 and on the wintering grounds Whistling Swans usually feed extensively on aqua- 

 tic plants (Johnsgard 1975, 1978). Stewart and Manning (1958) analyzed 49 stom- 

 achs of birds wintering on Chesapeake Bay. They found that 100% of the diet in 

 fresh estuarine waters consisted of submerged aquatic plants. In brackish 

 waters and estuarine marsh ponds these plants formed 60% and 49% of the diet, 

 respectively. In the Chesapeake Bay region wild celery ( Valisneria spiralis ) 

 was an "all-important" item of diet in fresh estuarine areas but widgeongrass 

 ( Ruppia maritima ) , sago pondweed ( Potamogeton pectinatus ) , and two bivalve mol- 

 luscs (long clam [ My a arenaria ] and Baltic macoma [ Macoma balthica ] ) were the 

 most important foods when all feeding habitats were considered (Stewart and 

 Manning 1958). Other plants eaten in the east include foxtail grass ( Alope- 

 curus ) , pondweeds ( Potamogeton spp.), squarestem spikerush ( Eleocharis quad - 

 rangulata ) , arrowhead ( Sagittaria ) and coontail ( Ceratophyllum demersum ) (Palmer 

 1976a). 



We have found little information on the diet of birds wintering in the 

 southeastern states. Presumably they feed on much the same foods as in Chesa- 

 peake Bay. Cely (1979) suggested that the principal foods in South Carolina 

 were widgeongrass and muskgrass ( Chara sp.). In the winter of 1969-70, swans 

 foraged in fields on the wintering grounds near Chesapeake Bay to a much greater 

 extent than formerly; we do not know whether this trend continued nor how im- 

 portant waste grain may be in the diet of Whistling Swans wintering in the 

 southeast. Johnsgard (1975), Bellrose (1976), and Palmer (1976a) summarized 

 what little is known of food habits elsewhere in North America. 



IMPORTANT BIOLOGICAL PARAMETERS 



Egg Laying Time of laying at any particular locality may vary consider- 

 ably from year to year (Palmer 1976a) but is usually remarkably synchronous 

 within any given season (Bellrose 1976). Egg laying usually begins in late May 

 or early June (Johnsgard 1975, Palmer 1976a) and in some areas nests with eggs 

 have been found as late as mid-July (Palmer 1976a) . 



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