Both mallards and black ducks are year- 

 round residents of New England. The black 

 duck is currently more abundant, but there 

 is evidence that it is hybridizing with 

 and being replaced by the northward spread 

 of the closely related mallard. Black 

 ducks use tidal flats, especially in 

 northern New England, more than any other 

 species of this group. Breeding in 

 freshwater swamps, marshes, and streams 

 throughout New England, black ducks 

 migrate to the coast in the fall and rely 

 heavily on tidal flats during the winter. 

 Winter feeding may be regulated by tidal 

 rhythms and' weather and although these 

 ducks are mainly herbivorous, their diet 

 includes intertidal invertebrates such as 

 the blue mussel ( Myti lus edulis ), soft- 

 shelled clam ( My a ar enaria ), and sand worm 

 ( Nereis virens ) and various amphipods and 

 isopods (Hartman 1963). During severe 

 winter weather, black ducks remain in 

 groups in open water kept free of ice by 

 tidal currents (Spencer et al. 1980). 



5.6 RAPTORS 



As consumers of large fish and shore- 

 birds, the hawks and eagles (family Accip- 

 itridae), and osprey (family Strigidae) 

 occupy the highest level in the nearshore 

 food chain. Of these raptors, the osprey, 

 and bald eagle exceed all others in terms 

 of their dependence on the coastal zone. 

 Ospreys eat a variety of coastal pelagic 

 fish and often hunt over shallow water 

 where they can take more demersal varie- 

 ties. Prey species weigh up to 2 kg 

 (4 lb) (Bent 1937) and there have been 

 reports of these birds being drowned while 

 attempting to capture large fish. The 

 osprey soars 30 m (100 ft) or more above 

 the water, where with its keen eyesight, 

 it may locate even the most camouflaged 

 species such as flatfish. When prey is 

 detected, the soaring is often interrupted 

 by hovering which may last up to ten 

 seconds and is usually followed by a 

 spiral plunge into the water. Prey is 

 captured with specialized talons and car- 

 ried in flight always with the head point- 

 ing forward to reduce frictional drag 

 (Terres 1980). Hovering is an important 

 behavioral adaptation. Although an ener- 

 getic cost is involved, dives from hovers 

 are 50% more successful than those started 

 from a glide (Grub 1977). 



Ospreys nest along most of the Maine 

 coast and at several locations in southern 

 New England, often forming loose colonies. 

 Telephone poles, trees, channel markers, 

 duck blinds, chimneys, and man-made nest- 

 ing platforms are all acceptable locations 

 for their huge nests that may weigh up to 

 455 kg (1000 lb) (Abbott 1911, in Terres 

 1980). These birds are protected by law 

 and although presently on the increase, 

 their numbers in New England have reached 

 precariously low levels during this cen- 

 tury. The decline of the osprey is due to 

 coastal development, human disturbance, 

 and eggshell thinning and embryo mortality 

 as a result of poisoning by DDT and other 

 chlorinated hydrocarbons. Puleston (1975) 

 reviewed the historical status of the spe- 

 cies on Gardiner's Island in Long Island 

 Sound. In 1932, there were 300 nests on 

 the island, representing what was probably 

 the world's greatest concentration of 

 nesting ospreys. In the 1940 's, the 

 colony seemed to be in good health; the 

 productivity of each nest averaged two 

 fledgings. A decline began in 1948 so 

 that by 1965 there were only 55 to 60 

 nests that were producing 0.07 young per 

 nest. Since then and coinciding with a 

 nationwide ban on many pesticides, fledg- 

 ing success has increased, and in 1974, a 

 total of 26 young were produced from 34 

 nests. Puleston (1975) believes that the 

 current modest increases in the New Eng- 

 land osprey population will continue. 



The bald eagle nests and winters in 

 Maine. Coastal areas support 75% of the 

 resident breeding and wintering popula- 

 tions and are used by spring and fall 

 migrants (Famous et al. 1980). Most eagle 

 nests are close to bays or estuaries where 

 the birds can obtain their preferred diet 

 of fish (tomcod, sculpin, alewives, blue- 

 black herring, and American eels) (Famous 

 et al. 1980). During the winter, eagles 

 depend increasingly on birds as their 

 major prey. The remains of 20 different 

 species of seabirds have been recorded as 

 eagle prey, of which black ducks and gulls 

 constitute more than 50% (Famous et al. 

 1980). Like the ospreys, the terminal 

 position of the eagle in the food chain 

 has resulted in decreased breeding success 

 due to toxic chemical poisoning. Studies 

 of Maine bald eagle eggs from 1967 to 

 1979 indicated an average shell thickness 

 15% less than normal and no significant 



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