Manitoba tended to forage in open water near the center of ponds (Siegfried 

 1976b). Young birds usually feed on well-vegetated ponds intermediate in size 

 between those used for nesting and those used for resting (Trauger and Stoudt 

 1974 in Bellrose 1976). In addition, they often feed on open water far from 

 the nest site (Palmer 1976b). Migrants gather on large freshwater lakes and 

 marshes where aquatic plants are abundant (Johnsgard 1978). 



Winter and Offshore Johnsgard (1978) reported that preferred winter hab- 

 itat consisted of brackish estuarine bays rather than either salt or fresh 

 water. Palmer (1976b) noted that Canvasbacks regularly feed in shallow water 

 after flying in from roosting areas on open bays and lakes. These roosting 

 areas are usually well offshore, but Canvasbacks may come to shore when encount- 

 ering heavy winds. 



FOOD AND FEEDING BEHAVIOR 



Canvasbacks dive for food using their feet for propulsion; they feed most- 

 ly in the early morning and evening. In deeper water they dive for periods of 

 10-20 sec (Palmer 1976b). When diving, both this species and the Redhead lift 

 up the front of their body, arch their necks, and submerge vertically; they sub- 

 sequently rise to the water's surface near where they dove (Siegfried 1976b). 

 Siegfried (1976b) recorded mean diving times of 17.6 and 15.6 sec for males and 

 females, respectively, foraging on ponds in Manitoba. At coastal impoundments 

 in South Carolina, mean diving times varied from 13.1 to 15.3 sec in relation 

 to the depth of the water; there was no significant difference in diving times 

 between the sexes (Alexander and Hair 1979). Foraging rates (dives per 5 min- 

 utes) in the impoundments varied with depth of water and ranged from 1.7 to 

 10.0. Alexander and Hair (1979) noted that the Canvasbacks established and de- 

 fended individual foraging sites. 



In very shallow water this duck will also "puddle" with its feet and then 

 dip its bill to feed. Canvasbacks also seize insects from the water's surface 

 and from the air (Palmer 1976b). 



Summaries of Canvasback food habits by Bartonek and Hickey (1969a), Bell- 

 rose (1976), and Palmer (1976b) indicate that these ducks primarily feed on 

 plants but are not averse to feeding on animals. The extent to which plants 

 are utilized may vary considerably. Authors cited in Palmer (1976b) indicated 

 a consumption of 65% plant matter in Illinois, 74% at Reelfoot Lake in Tennes- 

 see, 95% in Missouri, and 80% over a large portion of the range. 



Pondweeds ( Potamogeton spp.), wild celery ( Vallisneria spiralis ), and wid- 

 geongrass ( Ruppia maritima ) are among the more important plant foods. Bartonek 

 and Hickey (1969a) believed that Potamogeton may be more important in the diet 

 than Vallisneria because the former occurs more widely within the range of the 

 Canvasback (this duck's specific name is derived from a supposed predilection 

 for Vallisneria ) ♦ Animal foods consist largely of various molluscs and aquatic 

 insects; crustaceans and fish may also be taken. Caddisfly larvae and cases 

 and midge (Chironomidae) larvae are among the insects frequently reported. 



Some Canvasbacks on the breeding grounds eat a much higher proportion of 



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