TROPHIC RELATIONS OF SEABIRDS 



113 



Table 14. Use of food resources by seabirds in the oceanic habitat, central subarctic domain. 

 Information is from Tables 1-10. (Trophic level I = plants, II = secondary carnivore, III = 

 tertiary carnivore, IV = upper level carnivore, Sc = scavenger on carrion, offal, or detritus 

 [II-IV]; x = major food in diet, o = minor food, = incidental food, ? = probable food.) 



some of the less abundant birds, the marine 

 ducks, which feed mostly on two prey 

 categories. 



The remaining seabirds are more general in 

 their feeding. Many have large populations, 

 but are not as abundant as shearwaters or 

 most alcids. The true "generalists" are the 

 species that feed on as many as eight or more 

 types of prey, and relatively few (12%) such 

 species exist in each avian community. These 

 birds, the scavengers, include black-footed 

 albatross, fulmar, storm-petrels, and large 

 gulls. The petrels are the scavengers of the 

 oceanic habitat and the gulls are their coun- 



terparts in the neritic habitat (but see Sanger 

 1973). 



Another comparison is shown in Table 17, 

 where the species in each community are cate- 

 gorized according to the number feeding at 

 each trophic level. If a species feeds at more 

 than one level, it is tallied once in each level. 

 Most seabirds (66-77%) feed at the second and 

 third levels as secondary and tertiary carni- 

 vores. Few feed as terminal carnivores, and 

 relatively few are scavengers. Actually, most 

 scavenging occurs at levels II and III, so 

 about 90% of the seabirds in each community 

 feed at levels II and III. Communities includ- 



