extremely important. Most species in this guild 

 ordinarily feed over shallow subtidal waters, but 

 some feeding is carried out over intertidal flats. 

 Many species seek particular characteristics in 

 their wintering habitat, prime among these being 

 suitable food densities. Certain shallow areas of 

 the Pamlico Sound are noted for their high scaup 

 abundances, probably because of relatively dense 

 populations of thin-shelled cVdms, Mulinia lateralis, 

 Macoma baltliica, and Macoma phenax. These 

 three species of clams contribute significantly to 

 the winter diet of most benthic-feeding ducks in 

 brackish waters in North Carolina. Fortunately, 

 the recruitment potential of these clams is high so 

 that there are fairly predictable supplies each 

 winter somewhere within the brackish waters of 

 North Carolina (Williams 1978). Bufflehead, in 

 contrast, seem to prefer the more saline waters of 

 Bogue, Back, or Core Sounds, where they only 

 rarely encounter high clam densities. Although 

 many ducks congregate in multi-species flocks on 

 their wintering grounds, some degree of habitat 

 specificity remains, which, in combination with 

 the mobility of these birds, can make accurate 

 estimation of wintering populations difficult. 



5.7 BIRDS OF PREY 



The most obvious of the birds of prey along 

 the shorelines of North Carolina's sounds, lagoons, 

 estuaries, and river mouths is the osprey. These 

 large predators can often be seen soaring at alti- 

 tudes of up to 60 meters. From this height they 

 plummet down to capture fish with their talons. 

 Because of their large body size, they normally 

 take relatively large fish, including adult mullet, 

 bluefish, and eels. Ospreys nest along shorelines in 

 coastal North Carolina and are fairly common in 

 several localities. They often fish in shallow wa- 

 ters, occasionally over intertidal habitats, perhaps 

 for the same reasons that terns concentrate their 

 searching in these areas. Even bottom fishes can 

 be captured in shallows, where land masses help 

 block the wind, smoothing the water surface for 

 clearer visibility. Although ospreys are not direct- 

 ly dependent upon intertidal flats, many of the 

 fish which they consume have used the intertidal 

 flat as a feeding ground. 



The bald eagle is another bird of prey which 

 lives almost exclusively on a diet of fish. There 

 have been several confirmed sightings of bald ea- 

 gles from coastal North Carolina, but this species 

 is unquestionably rare. When it does appear in 

 coastal North Carolina, sightings usually decrease 

 during winter. The bald eagle fishes in shallow 

 coastal waters, even over intertidal flats. It also 

 scavenges dead fish. 



Various hawks are known to take an occa- 

 sional shorebird in their diets. One relatively 

 abundant hawk during winter in coastal North 

 Carolina, the marsh hawk, preys heavily upon ro- 

 dents and sometimes on the smaller shorebirds. It 

 is also possible that some small shorebirds fall 

 prey to owls. The barn owl and the short-eared 

 owl arc often seen hunting near the marshes of 

 North Carolina during the winter. 



5.8 GENERAL COMMENTS 



In the preceeding analysis of the birds of in- 

 tertidal habitats, one group whose members fly 

 over intertidal flats has been omitted. Purple mar- 

 tins and other swallows are extremely common in 

 coastal North Carolina during the summer. These 

 birds are insectivorous and can be seen 'hawking' 

 insects over intertidal flats. These species have 

 been excluded from Table 4 because most of the 

 insects captured over intertidal flats actually 

 come from other environments, including espe- 

 cially the salt marsh (see Davis and Gray 1966 for 

 an analysis of the insects of a North Carolina salt 

 marsh). The link between intertidal flats and the 

 swallows is weak and relatively insignificant. 



For the birds of Table 4 as a group, the inter- 

 tidal flat habitat is extremely important. For wa- 

 ders, and both the deep and shallow probers, this 

 habitat is critical to their continued survival be- 

 cause they feed there almost exclusively. For the 

 molluscivorous ducks, intertidal flats are almost 

 as important. In contrast, if intertidal flats were 

 eliminated by channelization or some other pro- 

 cess, most species of fishes and invertebrates 

 would survive by virtue of their utilization of sub- 

 tidal environments. 



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