Conservation of marine birds of northern North America: / papers from the international symposium held at the Seattle Hyatt House

by Unknown

Table 11. Use of food resources by seabirds in the Bering Sea coastal domain. Information is from Tables 1-10. (Trophic level I = plants, II = secondary carnivore, III = tertiary carnivore, IV = upper level carnivore [on birds only in this table], Sc = scavenger on carrion, offal, or detritus [II-IV]; x = major food in diet, o = minor food, * = incidental food, ? = probable food.)

Seabirds	Habitat, bird trophic levels (I-IV. Sc), and food categories
	Oceanic and offshore neritic									Inshore neritic
	II				III		IV	Sc	I	II						III			IV	Sc
	C r u s t a c e a n	P o l y c h a e t e	C o e l e n t e r a t e	F i s h / s q u i d e g g s & l a r v a e	F i s h	C e p h a l o p o d	B i r d s	C a r r i o n / o f f a l / d e t r i t u s	P l a n t	C r u s t a c e a n , m i d w a t e r	C r u s t a c e a n , b e n t h i c	C o e l e n t e r a t e	E c h i n o d e r m	M o l l u s c	F i s h / s q u i d e g g s & l a r v a e	F i s h , m i d w a t e r	F i s h , b e n t h i c	C e p h a l o p o d	B i r d s	C a r r i o n / o f f a l / d e t r i t u s
Gavia adamsii											*					o	x
G. arctica																o	x
Podiceps grisegena											o					o	x
Diomedea nigripes	x	o	o	o	x	x		x
Fulmarus glacialis	x	o	x	o	x	x		x
Puffinus griseus	x				x	x										o		o
P. tenuirostris	x				o	x										o		o
Oceanodroma furcata	x	o	o	x	x	x		x
Phalacrocorax auritus											o					x	o
P. pelagicus											x						x
P. urile											x						x
Branta bernicla									x
Philacte canagica									x
Clangula hyemalis										o	x			o			o
Histrionicus histrionicus										o	x			o
Polysticta stelleri									o	x	o			o
Samateria mollissima											x		o	x
S. spectabilis									o		o		o	x
S. fischeri									x					x
Melanitta deglandi														x	o
M. nigra									o		o			x
Haliaeetus leucocephalus																x			x	x
Falco peregrinus																			x
Phalaropus fulicarius	x			x				o		x					x
Lobipes lobatus	x			x				o		x					x
Stercorarius spp.	o				x	x	?	x								x			x	x
Larus hyperboreus	o			o	o	o			o		o	o	o	o	o	x			x	x
L. glaucescens	o			o	o	o			o		o	o	o	o	o	x			x	x
L. argentatus	o			o	o	o			o		o	o	o	o	o	x			o	x
L. canus											x	o	o	o	x					x
Rissa tridactyla	x				x	x			o
Xema sabini	x			x	o	o
Sterna paradisaea	x			x	o	o
Uria aalge	x	o			x	x				o	o					x	o
U. lomvia	x	o			x	x				o	x					o	x
Lunda cirrhata	?				x	x
Fratercula corniculata		*			x	x
Cepphus columba											o						x	o
Synthliboramphus antiquus	x				x					o
Brachyramphus brevirostris										x						o
Cyclorrhynchus psittaculus	x	o		*	*
Aethia cristatella	x			x
A. pusilla	x			o

Table 12. Use of food resources by seabirds in the oceanic and offshore neritic habitats, Bering Sea 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.)

Seabirds	Bird trophic levels and food categories
	II				III		IV	Sc
	Cru­sta­ce­an	Po­ly­chae­te	Coe­len­te­ra­te	Fish/Squid eggs & Lar­vae	Fish	Ce­pha­lo­pod	Birds	Car­ri­on/of­fal/de­tri­tus
Diomedea nigripes	x	o	o	o	x	x		x
D. immutabilis						x
Fulmarus glacialis	x	o	x	o	x	x		x
Puffinus griseus	x				x	x
P. tenuirostris	x				o	x
Pterodroma inexpectata					x			x
Oceanodroma furcata	x	o	o	x	x	x		x
Phalaropus fulicarius	x			x				o
Lobipes lobatus	x			x				o
Stercorarius spp.	o				x	x	?	x
Larus hyperboreus	x	o	o	o	x	x	?	x
L. glaucescens	x	o	o	o	x	x	?	x
Rissa tridactyla	x				x	x		o
R. brevirostris	x				x	x		o
Xema sabini	x			x	o	o
Sterna paradisaea	x			x	o	o
Uria aalge	x	o			x	x
U. lomvia	x	o			x	x
Lunda cirrhata	?				x	x
Fratercula corniculata		*			x	x
Synthliboramphus antiquus	x				x
Cyclorrhynchus psittaculus	x	o		*	*
Aethia cristatella	x			x
A. pusilla	x			o
A. pygmaea	x

Information contained in Tables 11-15 can be summarized to show characteristics of seabird trophic relations. One such characteristic is the range of diet breadth or diet complexity (Table 16). Few species (about 6%) feed on only one type of prey and might, therefore, be referred to as "specialists." Included are eared grebe (Podiceps caspicus), Laysan albatross, brown pelican, emperor goose (Philacte canagica), black brant (Bernicia bernicla), peregrine falcon, and whiskered auklet (Aethia pygmaea). Consideration of these species as specialists may require revision when more data become available. Except for the albatross and auklet, these species are members of the inshore neritic cohort. Food specialization does not seem to be characteristic of oceanic birds in particular or of most seabirds in general.

Table 13. Use of food resources by seabirds in the Alaska Stream 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.)

Seabirds	Habitat, bird trophic levels (I-IV. Sc), and food categories
	Oceanic and offshore neritic									Inshore neritic Inshore neritic
	II				III		IV	Sc	I	II						III			IV	Sc
	C r u s t a c e a n	P o l y c h a e t e	C o e l e n t e r a t e	F i s h / s q u i d e g g s & l a r v a e	F i s h	C e p h a l o p o d	B i r d s	C a r r i o n / o f f a l / d e t r i t u s	P l a n t	C r u s t a c e a n , m i d w a t e r	C r u s t a c e a n , b e n t h i c	C o e l e n t e r a t e	E c h i n o d e r m	M o l l u s c	F i s h , m i d w a t e r	F i s h , b e n t h i c	C e p h a l o p o d	B i r d s	F i s h / s q u i d e g g s & l a r v a e	C a r r i o n / o f f a l / d e t r i t u s
Gavia immer										*					x	x
G. adamsii										*					o	x
G. stellata										*					o	x
Podiceps grisegena										o					x	o
Diomedea nigripes	x	o	o	o	x	x		x
Fulmarus glacialis	x	o	x	o	x	x		x
Puffinus griseus	x				x	x									o
P. tenuirostris	x				o	x									o
Pterodroma inexpectata					x			x
Oceanodroma furcata	x	o	o	x	x	x		x
Phalacrocorax auritus										o					x	o
P. pelagicus										x						x
P. urile										x						x
Philacte canagica								x
Clangula hyemalis									o	x			o
Histrionicus histrionicus									x	x			o
Polysticta stelleri								o	x	o			o
Somateria mollissima										x		o	x
S. spectabilis										o		o	x
S. fischeri								x					x
Melanitta deglandi													x	o
M. perspicillata								o					x	o
M. nigra								o		o			x
Mergus serrator										o					x	x
Haliaeetus leucocephalus																x			x	x
Falco peregrinus																		x
Phalaropus fulicarius	x			x				o	x								x
Lobipes lobatus	x			x				o	x								x
Stercorarius spp.	o				x	x	?	x								x			x	x
Larus hyperboreus	o			o	o	o		o			o	o	o	o	o	x			x	x
L. glaucescens	o			o	o	o		o			o	o	o	o	o	x			x	x
L. argentatus	o			o	o	o		o			o	o	o	o	o	x			o	x
L. canus											x	o	o	o	x					x
Rissa tridactyla	x				x	x		o
R. brevirostris	x				x	x		o
Sterna paradisaea	x			x	o	o				x						o
S. aleutica										x						o
Uria aalge	x	o			x	x				o	o					x	o
U. lomvia	x	o			x	x				o	x					o	x
Lunda cirrhata	?				x	x
Fratercula corniculata		*			x	x
Cepphus columba											o						x	o
Brachyramphus marmoratus										x					o	x
B. brevirostris										x						o
Synthliboramphus antiquus	x				x					x
Cyclorrhynchus psittaculus	x	o		*	*
Aethia cristatella	x			x
A. pusilla	x			o
A. pygmaea	x

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.)

Seabirds	Bird trophic levels and food categories
	II				III		IV	Sc
	Crustacean	Polychaete	Coelenterate	Fish/squid eggs & larvae	Fish	Cephalopod	Birds	Carrion/offal/detritus
Diomedea nigripes	x	o	o	o	x	x		x
D. immutabilis						x
Fulmarus glacialis	x	o	x	o	x	x		x
Puffinus carneipes	o				x	x
P. griseus	x				x	x
P. tenuirostris	x				o	x
Pterodroma inexpectata					x			x
Oceanodroma furcata	x	o	o	o	x	x		x
O. leucorhoa	x	o	o	o	x	x		x
Phalaropus fulicarius	x			x				o
Lobipes lobatus	x			x				o
Stercorarius spp.	o				x	x	?	x
Larus hyperboreus	x	o	o	o	x	x	?	x
L. glaucescens	x	o	o	o	x	x	?	x
L. argentatus	x	o	o	o	x	x		x
Rissa tridactyla	x				x	x		o
Xema sabini	x			x	o	o
Sterna paradisaea	x			x	o	o
Uria aalge	x	*			x	x
U. lomvia	x	*			x	x
Lunda cirrhata	o				x	x
Fratercula corniculata		*			x	x
Cerorhinca monocerata	x				x
Synthliboramphus antiquus	x				x
Cyclorrhynchus psittaculus	x	o		*	*
Ptychoramphus aleuticus	x			o

Most species (roughly 53% in any community) include two or three prey categories in their diets—usually midwater schooling fish, squid, and crustaceans. These birds include the most numerous in the communities—the shearwaters and some alcids—which feed largely on three prey types, and also include 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 counterparts in the neritic habitat (but see Sanger 1973).

Another comparison is shown in Table 17, where the species in each community are categorized 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 carnivores. 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 including an inshore neritic feeding element are the only ones that include herbivores, and even then, few of these species exist in significant numbers in the marine environment (discounting estuaries and sheltered bays).