Canvasbacks prefer plant materials, but also eat 

 many forms of animal life when available (Bellrose 

 1974). Canvasbacks traditionally wintered on Fearman 

 Lake in Vermilion Parish and fed on banana waterlily 

 but tlie plant gradually disappeared from the lake and 

 the canvasbacks moved to other wintering sites 



Most hooded mergansers are migratory, however, a 

 few birds remain on the Chenier Plain to nest. They nest 

 in tree cavities and often compete with wood ducks for 

 nest sites (Lowery 1974a). The shortage of nesting sites 

 sometimes is limiting to reproduction in the Chenier 

 Plain. 



The canvasback nests in northern United States 

 and Canada. Marsh drainage there causes a serious loss 

 of nesting habitat. 



5.3.52 LESSER SCAUP (Aythya affmis) 



The Chenier Plain and its offshore waters is a major 

 wintering area for lesser scaup. The species arrives in 

 the Chenier Plain in late October and forms flocks of 

 several thousand birds each in the Gulf of Mexico 1 to 

 10 km (0.6 to 6 mi) offshore. These combined flocks 

 number nearly 250,000 birds, of which an estimated 2% 

 may be greater scaup. Scaup remain offshore through- 

 out most of the early winter and usually move to inland 

 waters in January. During some years the scaup will 

 remain offshore until spring migration in March 

 (Chabreck et al. 1974b). 



The lesser scaup is typically a bird of large open 

 bodies of water, but at times it is found on small marsh 

 ponds. This species freely utilizes fresh, brackish, and 

 saltwater habitats. An excellent diver, it occasionally 

 feeds offshore in water over 6 m (20 ft) deep. 



The diet of lesser scaup consists largely of animal 

 material. Harmon (1962) examined 32 birds collected 

 5 to 7 km (3 to 4 mi) offshore from Cameron Parish and 

 found that 99.8% of the food eaten was surf clam 

 (Mullinia lateralis). Kimble (1958) examined 13 lesser 

 scaup killed on inland waters in Cameron Parish and 

 found that 75% of the diet was composed of animal 

 material, mainly small fish, clams, snails, and shrimp. 



Lesser scaup wintering on the Chenier Plain have a 

 nesting range which extends from the Dakotas north- 

 ward through the Canadian prairies into Alaska. The 

 species is greaUy affected by marsh drainage. 



5.3.53 HOODED MERGANSER (Lophodytes 

 cucullatus) 



Migrant hooded mergansers begin arriving on the 

 Chenier Plain in mid-october, but the major influx does 

 not take place until November. Largest numbers of 

 birds are present in mid-December. They begin depart- 

 ing in January and by March most have left the area 

 (Smith 1961). 



This species occupies marsh ponds and lakes. A 

 larger relative, the red-breasted merganser, limits its 

 activities to coastal bays and the Gulf of Mexico. 

 Hooded mergansers are often found on small ponds, 

 bayous, and canals and frequently occur in swamp for- 

 est habitat (Smith 1961). They consume a variety of 

 aquatic animals, but feed largely on fish. They catch 

 their prey by diving and by pursuing it underwater. Be- 

 cause of their diet, they are often referred to as 'fish 

 ducks' and are generally avoided by hunters (Lowery 

 1974a). 



5.3.54 LIMITING FACTORS FOR WATERFOWL 



The drainage of marshes is the major limiting fac- 

 tor affecting mallards and other migratory waterfowl in 

 the Chenier Plain and in the nesting grounds of the up- 

 per great plains of the U.S. and in Canada. Severe 

 weather conditions and drought also are factors affect- 

 ing nesting success and the size of fall populations in any 

 one year. 



Hunting removes a sizable portion of the fall popu- 

 lation, but the length of the hunting season and bag 

 limits are carefully regulated to help assure an adequate 

 nesting populationthe following summer. 



Disease outbreaks occur periodically in waterfowl 

 on the Chenier Plain, but are usually localized and in- 

 volve only a small number of birds. The major disease 

 is botulism and losses of up to 500 ducks have been re- 

 ported (Crain and Chabreck 1960). The disease usually 

 occurs in late summer and mottled ducks have been the 

 main species affected. 



Parasites are common in most species of ducks and 

 geese, but no mortality has been reported for the 

 Chenier Plain. Sarcocystis rileyii, a sporozoan, occurs in 

 a high percentage of the resident adult duck population 

 of the Chenier Plain; however, no adverse effects have 

 been noted among parasitized birds (Chabreck 1964b). 



Lead poisoning in waterfowl, caused by ingestion 

 of lead shot, is a major problem throughout most of 

 North America. Spent shot accumulates on feeding 

 areas as a result of decades of hunting. Shot ingested by 

 ducks and geese during feeding concentrates in the giz- 

 zard and is gradually eroded by the digestive processes. 

 Lead salts are released and then absorbed into the bird's 

 blood, often causing paralysis and death (Bellrose 

 1974). The death of 2,000 snow geese in rice fields 

 north of Lacassine National Wildlife Refuge in 1973 was 

 attributed to lead shot poisoning (Bateman 1975b). 

 Soft iron shot is gradually being substituted for lead and 

 should greatly reduce waterfowl losses in the future. 



Predators capture some waterfowl on the Chenier 

 Plain, but most adult birds taken are probably cripples. 

 Mottled ducks lose many eggs to raccoon predation 

 (Singleton 1953). Chabreck and Dupuie( 1976) reported 

 alligator predation on nesting Canada geese. Some ducks 

 are taken by avian predators. 



In the Chenier Plain, habitat loss has had some ad- 

 verse effect upon wintering waterfowl. Pabnisano 

 (1972a) found that ducks primarily used fresh marsh 

 habitat; therefore, marsh drainage or saltwater intrusion 

 would reduce its value for ducks. Special management 

 has been implemented on refuges and private duck clubs 

 to curtail saltwater intrusion and prohibit excessive 



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