FOOD AND FEEDING BEHAVIOR 



Redheads feed in marshes, sloughs, and ponds that are often only a meter 

 or so deep. When in deeper waters they dive for food, but in the shallows they 

 either "tip-up" or forage from the surface (Bellrose 1976). Alexander and Hair 

 (1979) reported some elements of foraging behavior on coastal impoundments in 

 South Carolina. Redheads usually foraged in small groups of 4-6 birds. At 

 Huntington Beach, they dove for an average of 15 sec and moved underwater an 

 average of about three body lengths. The mean foraging rate (defined as the 

 number of dives or tip-ups per 5-minute interval) varied from 4.2 at one local- 

 ity to 13.9 at another; no difference in foraging rate between the sexes was 

 noted . 



Redheads feed largely on vegetable food; studies cited by Palmer (1976b) 

 and Bellrose (1976) indicated that between 78% and 94% of the diet may consist 

 of plant material in transient and wintering areas. On the breeding grounds in 

 Manitoba, however, Redheads ate considerably more animal food (Bartonek and 

 Hickey 1969a) . The principal animal food consumed in this area was the larvae 

 of caddisflies (Trichoptera) . 



We give below a state-by-state summary of the principal foods eaten in the 

 southeast; more detailed information on specific foods consumed in other parts 

 of the range may be found in Palmer (1976b) and Bellrose (1976). 



North Carolina The food eaten by 44 Redheads wintering in Currituck 

 Sound was similar to that ingested by Canvasbacks in the same area but incorpo- 

 rated a larger proportion of southern naiad ( Najas guadalupensis ) and a smaller 

 proportion of pondweed ( Potamogeton spp.)(Quay and Critcher 1965). Pondweeds 

 accounted for 41.1% (by volume) of the food, southern naiad 21.9%, and widgeon- 

 grass ( Ruppia maritima ) , 12.9%. These three plant genera made up about 76% of 

 the food identified. Unidentified animals and plants made up 2.2% and 19.0%, 

 respectively, of the total material examined. 



Florida Stieglitz (1967) reported the foods consumed by 10 Redheads 

 wintering at Apalachee Bay, St. Marks NWR, on the Florida Gulf coast. Shoal- 

 grass ( Diplanthera wrightii ) was the principal food eaten, making up 85.3% of 

 the diet; the only other plant eaten was manateegrass ( Cymodocea manatorum - 

 0.7%), and it was found in only one Redhead. The rest of the food consisted of 

 molluscs, principally Olivella mutica (9.2%), Prunum apicinum (2.0%), Nassarius 

 ambiguus (1.0%), and Anachis avara (1.0%). 



Texas McMahan (1970) reported on the foods of 104 Redheads collected 

 from November through December on the Lower Laguna Madre. As in Florida, shoal- 

 grass was the principal food eaten and comprised almost an identical proportion 

 of the diet (84.2%). Widgeongrass (9.8%) was the only other plant eaten. Ani- 

 mal food consisted of snails (2.0%) and clams (0.1%). McMahan pointed out that 

 many of the snails were fossils that presumably had been picked up for grit and 

 suggested that Redheads probably fed to a greater extent on widgeongrass than 

 was indicated by his analysis of stomach contents. 



During the winter of 1974-75, Cornelius (1977) conducted another study of 

 the food habits of Redheads on the Lower Laguna Madre, following a decreased 



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