The downy young feed at or above the water surface for 1 to 2 weeks; some of 

 the food items described by Reinecke (1977) were chironomid (midge) pupae and 

 adults, spiders, caddisflies, and mayflies. Aquatic invertebrates constitute 

 about 90% (dry weight) of the diet of the young through the first 6 weeks of 

 life. Snails, clams, mayflies, caddisflies, sowbugs , and fly (Diptera) larvae 

 are an excellent source of highly digestible energy and protein for the young 

 during rapid growth (2-10 weeks). By the age of 8 weeks the juveniles are 

 consuming a diet higher in plant seeds and tubers and are making their first 

 flights. In late summer the juveniles wander about, primarily on inland 

 waterways (personal commuication from J. K. Ringelman, School of Forest 

 Resources, University of Maine, Orono, ME.; June, 1978). The females that 

 raised broods often remain at the breeding areas after the fledglings have 

 gone. The adults undergo postnuptial molt of flight feathers at this time and 

 may remain flightless until late September. 



Black duck migration begins in August just after they regain their flight 

 feathers. Many move down the major river systems toward the coast in fall. 

 Some winter on the Maine coast and others winter south as far as North 

 Carolina (Geis et al. 1971). Migration occurs principally during October and 

 November and most reach their wintering grounds by early December. 



Coastal Maine, which contains extensive black duck winter habitat, supported 

 about 92% of Maine's wintering black duck population during January, 1979. 

 The homing of black ducks to specific wintering areas or to breeding marshes 

 in spring is equally strong (Spencer and Corr 1977). During winter the birds 

 spend most of their time feeding and resting. Winter feeding is regulated 

 somewhat by the tidal rhythms and weather conditions. Winter foods (Hartman 

 1963) include intertidal invertebrates such as the edible mussel ( Mytilus ) , 

 soft-shell clam ( Mya ) , sandworms ( Nereis ) , amphipods ( Gammarus , Orchestia ) , 

 and isopods ( Idothea ) . 



During severe weather, feeding birds remain in open water areas kept free of 

 ice by the strong tidal currents. Winter is a period of high stress for black 

 ducks on the Maine coast. Both adult and immature birds lose weight at this 

 time. Reinecke (1977) estimated black ducks may starve in only 3 to 7 days if 

 severe ice conditions prevent feeding. 



Courtship activity and pair formation for the black duck begin in the fall and 

 occur through the winter on warm sunny days. With increasing temperatues in 

 February, courtship increases sharply and most birds are paired by the time 

 spring migration brings the birds back to the nesting marshes. 



15-46 



