North Carolina Seabird Helminths 63 



natant was decanted into another dish for examination with a stereo- 

 scopic microscope. All original sediment was washed repeatedly and 

 decanted as above. Gross examination of intestinal tissue was made in 

 an attempt to find attached helminths. Trematodes, cestodes, and acan- 

 thocephalans were fixed and stored in AFA (Alcohol-Formalin-Acetic 

 Acid), stained with Semichon's acetocarmine, cleared in methyl salicy- 

 late, and mounted in Kleermount. Nematodes were fixed in 70 percent 

 alcohol, stored in glycerin-alcohol, cleared in glycerin, and mounted in 

 glycerin jelly. 



RESULTS AND DISCUSSION 



Nine species of parasites were recovered (Table 1). One species of 

 digenetic trematode and one species of acanthocephalan were recovered 

 from the common tern; five species of cestodes were found in various 

 species of procellariiforms, and one species in the red-billed tropicbird; 

 and one species of nematode was found in two Wilson's storm petrels. 

 No helminths were recovered from the one black-capped petrel, Ptero- 

 droma hasitata, or the seventeen bridled terns, Sterna anaethetus, 

 examined. 



Sea birds vary greatly in the degree to which they are associated 

 with the open sea. Truly pelagic species may encounter land only during 

 breeding periods, while others, such as some species of gulls and terns, 

 may live and feed inshore except during migrations. Resulting differen- 

 ces in habits will affect exposure to the helminth fauna. 



Although fish probably represent a major food item for most spe- 

 cies examined, the coast-inhabiting terns also secondarily eat a variety 

 of crustaceans, insects, worms, and molluscs (Watson 1966). The acan- 

 thocephalans found in common terns probably used crustacean inter- 

 mediate hosts (Reish 1950; McDonald 1969). In 2 individuals the 

 number of acanthocephalans recovered exceeded 200, thus indicating 

 extensive feeding on the intermediate host. 



The procellariiform and pelecaniform hosts are all pelagic and 

 primarily consume fish and squid (Watson 1966, 1975). The tetrabo- 

 thriid cestodes and the heterocheilid nematode, Contracaecum sp., were 

 probably transmitted through fish or squid intermediate hosts (Baer 

 1954; Ellis and Williams 1973; Yamaguti 1959). However, the cestode, 

 Choanotaenia sp., recovered from Wilson's storm petrel, is from a genus 

 known to use insects as intermediate hosts (Yamaguti 1959). Infections 

 may have occurred during breeding, perhaps by ingestion of infected 

 insects associated with the nesting sites. 



A high prevalence of infection may best be explained by birds defe- 

 cating in an area where suitable intermediate hosts are present and their 

 ingestion is likely. A highly prevalent helminth might tend to be less 



