on slight ridges well above high tides. A second type is 

 inland prairies, including ungrazed areas such as aban- 

 doned fields, roadsides, levees and other sites having 

 dense cover. A third type is rice fields, either fallow or 

 in production. Only lightly grazed or completely un- 

 grazed fields are used. A few nests are located on levees, 

 but most are constructed in heavy patches of stubble. 

 Nests in stubble are poorly concealed compared to those 

 in dense saltmeadow cordgrass. Nest distance from 

 permanent or semipermanent water bodies was as far as 

 300 m (984 ft.). 



Flooding of nests is often a serious problem. Losses 

 are greatest after a dry spring when the ducks nest on 

 low sites that are flooded by heavy rainfall. During high 

 water ducks nest on higher sites. 



Although coastal marshes used by nesting ducks 

 have undergone changes during the past few decades. 

 Lynch (1967) felt that no great harm to mottled ducks 

 has resulted. The building of oilfield roads, cattle 

 walkways, and canals in the marshes of the Chenier 

 Plain seemed to have benefited rather than hurt nesting 

 ducks by providing flood-proof nest sites and drought- 

 proof rearing ponds. 



Although nesting does not peak until April, pair 

 formation takes place in early winter, and nesting may 

 begin as early as February (Singleton 1953). Clutch size 

 varies from 7 to 14 eggs and the incubation period is 

 about 26 days. Nest abandonment is common among 

 mottled ducks. Females that are disturbed early in egg- 

 laying (less than 5 eggs) will usually abandon the nest 

 but they renest readily. Singleton (1953) reported that 

 one pair built 5 nests and laid 34 eggs in one season. 

 Usually one brood is reared each year. 



Singleton (1953) observed 108 nests' over a 4-year 

 period (1949 to 1952) and reported that slightly over 

 25% of the nests were successful. Nests or eggs were 

 destroyed in rice fields mainly by raccoons, opossums, 

 dogs, cattle, and humans. As a part of the same study, 

 mortality in 115 broods up to 8 weeks of age was 

 found to be 38%. 



5.3.42 GADVI ALL (Anas strepera) 



The gadwall, often referred to as 'gray duck' by 

 hunters, is a winter resident of the Chenier Plain, 

 although a small segment of the population may mi- 

 grate to the tropics in unusually dry years. Approxi- 

 mately 90% of the population of the Central and 

 Mississippi flyways winter in Gulf coast marshes. About 

 40% winter m the Chenier Plain (Smith 1961). 



The first major flight of gadwalls into the Chenier 

 Plain takes place between mid-October and the first 

 week of November. The peak migration is during the 

 last week of October. Numbers gradually decline 

 until mid-November, then stabilize somewhat through 

 the remainder of the winter. The November decline 

 possibly reflects some migration farther southward. 



Gadwalls feed primarily on submerged aquatic 

 plants. Migrants arriving in October concentrate in 



large flocks on shallow lakes in brackish marshes con- 

 taining dense stands of widgeongrass (Chabreck 1978). 

 The birds then disperse to other marsh lakes as food 

 supplies become depleted. 



Gadwalls show a strong preference for vegetative 

 parts of aquatic plants, including leaves and succulent 

 stems. Although seeds are consumed, they may often be 

 taken as a source of grit rather than food. This was 

 likely the case in Kimble's (1958) study in Cameron 

 Parish, where sawgrass made up 62%- of the gizzard 

 contents of gadwalls. He also found that widgeongrass 

 composed 27% of the contents and other plant foliage 

 made up 9%. Smith (1973) found the gadwall's diet to 

 consist of 35% waterweed, 33%^ spikerush, 22% algae, 

 and 10% aquatic plants. 



Gadwalls begin pair formation and courtship dur- 

 ing late winter in the Chenier Plain, but nesting and 

 brooding take place in the great plains and the lakes of 

 western mountains (Johnsgard 1975). Gadwalls nest 

 later than other dabbling ducks, and occasionally hens 

 do not enter the postnuptial molt until after the fall 

 migration to the Chenier Plain (Chabreck 1966b). 



5.3.43 NORTHERN PINTAIL {Anas acuta) 



Pintail migrants first arrive in the Chenier Plain in 

 mid-September. Numbers rapidly increase through Oc- 

 tober and November and peak in December. Many 

 flocks depart for wintering areas in Mexico and Cen- 

 tral America. The exodus results in lower populations 

 during midwinter, but the southerly migrants begin re- 

 turning by late January, and Chenier Plain populations 

 again increase (Smith 1961). The pintail is a mobile, 

 wide-ranging species that shifts readily from area to 

 area on wintering grounds. 



Early migrants are attracted to large shallow lakes 

 with abundant stands of aquatic plants. Brackish lakes 

 containing widgeongrass are favored areas in the Che- 

 nier Plain. In December and January, fresh and brackish 

 marshes with dense stands of annual grasses and sedges 

 are preferred feeding areas for the pintail. They usually 

 feed in water less than 30 cm (12 in) deep. After feed- 

 ing, pintails fly to rest areas where they concentrate in 

 large flocks (Tamisier 1976). 



Grasses compose the bulk of the pintail's diet. 

 Ninety-eight percent of the content of crops from birds 

 taken in the vicinity of Creole were grass seeds (Bard- 

 well 1962). Animal material made up less than 1% of 

 the diet. 



Most pintails wintering on the Chenier Plain are 

 paired prior to spring migration. Nesting and brood 

 rearing take place mostly in the prairie pothole region 

 of southern Canada. 



5.3.44 GREEN-WINGED TEAL {Anas crecca) 



The Chenier Plain is a major wintering area of the 

 green-winged teal. Birds begin to arrive in late Septem- 

 ber, but the major flights do not arrive until late Octo- 

 ber (Smith 1961). Populations continue to increase 



244 



