Table 2. Percentage of vegetative composition in manipulated freshwater impoundments and 

 adjacent freshwater marsh on Rockefeller Refuge in 1959 (data from Chabreck 1960). 



% Cover 



Species 



Marshhay cordgrass 



Wild millet 



Sprangletop 



Widgeongrass 



Waterhyssop 



Nutgrass 



Other 



Wildlife 



Manipulated freshwater impoundments are usually managed for dabbling ducks. A study by 

 Chabreck et al. (1974) found that year-round dabbling duck use of an impoundment was over 4 

 times that of an adjacent non-impounded marsh. Waterfowl use of impoundments was greatest 

 during the winter and the least during the summer, and was over 6 times greater in the impounded 

 area than in the control area during the winter. Duck use of an impounded area in southcentral 

 Louisiana during the winter was 9 times greater than usage in a control area (Carney and Chabreck 

 1977). 



In addition to waterfowl, other wildlife benefit from this type of management. Coots and rails 

 use this habitat quite heavily as long as water depths are favorable. Wading birds are attracted to 

 the impoundment by shallow water conditions. This impoundment type is highly preferred by most 

 fur animals, particularly species such as mink (Mustela vison), raccoon (Procyon lotor), and river 

 otter (Lutra canadensis) that feed on crawfish (Procambarus clarkii). Nutria also find this habitat 

 favorable. Alligators are attracted by the abundance of prey (Chabreck 1960), but early drying may 

 reduce nesting (Joanen and McNease 1978). 



Permanently Flooded Brackish Impoundments 



Plants. On Rockefeller Refuge, impoundments permanently flooded with brackish water consis- 

 tently produced an abundance of high quality duck foods, dominated by widgeongrass (Table 3). 

 A survey of marsh impoundments in South Carolina disclosed that the permanently flooded brackish 

 impoundments were the habitat most often used by ducks in that State (Morgan et al. 1975). 



Wildlife. The permanently flooded brackish impoundments are heavily used by gadwalls, 

 American widgeons, and lesser scaup {Aythya affinis), which are attracted to dense stands of 

 widgeongrass. These impoundments receive high use by coots, but wading birds and fur animals 

 avoid them because of water depth and lack of cover. Brackish marsh is not preferred alligator 

 habitat if water salinity becomes excessive (Chabreck 1960). 



Manipulated Brackish Impoundments 



Plants. In manipulated brackish impoundments, the most successful technique in South Carolina 

 involves a spring drawndown for 2 to 8 weeks, during which time the marsh is maintained in a 



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