small baitfishes (killifishes, silversides, anchovies). 

 Although present in coastal North Carolina, the 

 lesser yellowlegs is typically associated with im- 

 poundments and high marsh pools. Because it 

 very rarely visits intertidal flats, it is excluded 

 from Table 4. With the exception of the ibises 

 and the yellow-crowned night heron, the waders 

 are almost exclusively fish eaters. The white ibis 

 feeds largely upon crustaceans, including in par- 

 ticular fiddler crabs {Uca spp.) on North Carolina's 

 tidal flats. The yellow-crowned night heron con- 

 sumes a variety of smaller crustaceans as well as 

 some fishes. Some species of waders, such as the 

 green heron and the great blue heron, are frequent 

 foragers along the shorelines of ponds and other 

 freshwater habitats. Since the cattle egret feeds al- 

 most entirely on insects taken from pastures and 

 fields and since the glossy ibis feeds almost ex- 

 clusively in ponds on the high marsh, neither spe- 

 cies has been listed in Table 4 despite their obvi- 

 ous presence in coastal North Carolina. 



Because the herons, egrets, and ibises are 

 colonial nesters, breeding populations are easy to 

 estimate. Parnell and Soots (1978, 1979) have 

 made extensive studies of the rookeries of these 

 waders in North Carolina, from which excellent 

 population estimates are available. Almost all 

 heron, egret, and ibis rookeries (usually called 

 heronries for this group) occur on islands, probab- 

 ly because potential egg predators like foxes, ra- 

 coons, and rats are usually absent from islands. In 

 North Carolina, 61% of estuarine islands are arti- 

 ficial, composed of dredge spoil. Of the heronries, 

 62% occur on such dredge-spoil islands, and those 

 heronries on dredge-spoil islands are larger and 

 contain 92% of all nesting waders (Parnell and 

 Soots 1978). Parnell and Soots suggest that the 

 dredge-spoil island is a preferred site because such 

 islands are higher in elevation than natural islands 

 and, therefore, less subject to overwash and flood- 

 ing. Since most dredging is done near inlets where 

 fish are abundant, the spoil islands are ideal loca- 

 tions for fish-eating waders. 



The birds of any coastline can be divided into 

 at least four groups based upon their seasonal oc- 

 currence: (1) summer (breeding) residents; 

 (2) winter residents; (3) transients (passing through 

 during either fall or spring migrations or both); 

 and (4) permanent residents. All of the herons, 

 egrets, and the ibis listed in Table 4 summer and 

 breed in North Carolina, and most species spend 



the winter as well. The greater yellowlegs is the 

 only species in this guild which fails to breed in 

 North Carolina; it is a winter resident. The year- 

 round presence of wading birds is made possible 

 by the permanent presence of small baitfishes 

 over the tidal flats of North Carolina. Farther 

 north, where small fishes are rare on flats during 

 winter and where ice cover restricts access to 

 those fishes which are present, waders cannot 

 feed year-round. 



5.3 SHALLOW-PROBING AND SURFACE- 

 SEARCHING SHOREBIRDS 



Like the waders, this guild is typical of inter- 

 tidal habitats worldwide. It is also the most di- 

 verse and most abundant guild on many intertidal 

 flats, including those of North Carolina. Not only 

 is the species diversity of this guild high, but also 

 the diversity of form and structure. Bill lengths 

 and shapes vary widely, presumably correlated 

 with differences in prey type. Recher (1966) has 

 suggested that various species in this group possess 

 such a wide diversity of bill structures and feeding 

 habits as a means of coexistence in a habitat (the 

 intertidal flat) which itself cannot be adequately 

 partitioned because of its physical uniformity. In 

 other words, perhaps these probing and searching 

 species have specialized on certain food types and 

 certain foraging strategies in order to avoid com- 

 petitive exclusion because habitat segregation is 

 nearly impossible. 



The list of shallow-probing and searching 

 shorebirds of North Carolina's intertidal flats 

 (Table 4) includes all species that would ever be 

 encountered in this habitat, with two exceptions 

 (the pectoral sandpiper and the solitary sandpiper 

 which feed almost exclusively on sandy beaches). 

 Some of the species which appear on this list, 

 such as killdeer, golden plover, and long-billed 

 dowitcher, obtain only a small fraction of their ^ 

 food from intertidal flats. Killdeer often feed on 

 insects in fields. The majority of species listed in 

 this guild, however, depend upon the intertidal 

 flat for most of their food requirements (Palmer 

 1962). 



Shallow probers are extremely opportunistic 

 in their feeding, taking what food items are most 

 abundant. Diets of individual species differ radi- 

 cally over lime and in different localities. 

 Schneider (1978) constructed cages to exclude 



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