evaluated in Maine and their relationship as food for wintering bald eagles 

 particularly needs study. They often are prey for eagles and may well be 

 carrying heavy loads of pesticides and/or heavy metals accumulated from the 

 consumption of contaminated fish. The estuarine systems of the Penobscot and 

 Kennebec Rivers are areas of particular concern. 



CASE STUDY: THE BLACK DUCK 



This description of the biology and habits of the black duck, a species 

 nesting in freshwater wetlands of coastal Maine, is representative of the type 

 of information that should be developed for all major ducks of coastal Maine. 

 This species was selected because its breeding and wintering ecology have been 

 studied in Maine in considerable detail (Coulter and Miller 1968; Hartman 

 1963; Mendall 1949; and Reinecke 1977). This case study essentially describes 

 the arrival of the breeding pairs at the nesting area and their life through 

 the following spring. Excellent resumes of the life history of black ducks 

 (and other Maine waterfowl) are contained in Bellrose (1976b) and Palmer 

 (1976). 



After the breakup of winter ice, black ducks migrate from wintering areas 

 along the coast of Maine to northern breeding marshes in Maine and Canada. 

 Although the migrants travel in flocks, most birds pair before reaching the 

 breeding grounds. Although older adult females frequently return to marshes 

 they formerly used in previous breeding attempts (Coulter and Miller 1968), 

 yearling females are much less precise. Black ducks breed and nest mostly in 

 freshwater marshes, shrub swamps, beaver f lowages , woodland brooks, and 

 streams. The monthly activities (phenophases) of male and female black ducks 

 are shown in figure 15-12. 



Spring arrival dates vary according to the latitude of the breeding site and 

 weather conditions. In coastal Maine most birds arrive in late March through 

 mid-April. Within a week to 10 days after arrival the female examines 

 terrestrial nesting cover either from the water or afoot. Most nests are 

 constructed during the second week of April through the first week in May 

 (Coulter and Miller 1968). Soon after arrival at the breeding marsh, mated 

 pairs isolate themselves from others of their species and establish a 

 prenesting territory. At this time males become protective and aggressive. 

 They attempt to drive away other black duck males or pairs. Daily breeding 

 and nesting activities consist of feeding, resting, plumage maintenance, 

 courtship, copulation, and exploration of the breeding marsh. 



The development of the female ovary in preparation for egglaying begins about 

 7 days before the first egg is laid. At this time the female experiences a 

 change in nutritional requirements (Krapu 1977). Nesting ducks feed 

 extensively on aquatic invertebrates at this time (Swanson et al. 1977). 

 Although a vegetable feeder during much of the year, from 60% to 70% of the 

 female black duck diet consists of clams, snails, mayflies, caddisfly larvae, 

 sowbugs, and other invertebrates (Reinecke 1977). 



The nest site selected by the female normally provides overhead cover and has 

 sufficent ground litter available for her to dig a shallow cup in the ground 

 with her feet. Other characteristics of the nest site are highly variable. 

 The nest may be located on a floating bog mat, in the woods, or in a blueberry 

 field a thousand or more feet from the nearest water. In sedge-meadows, 



15-43 



10-80 



