Chapter VIII: Part V: , Birds. U.S. Army, Signal Corps, Washington, D.C. Pages (2)

Literature on the diets of seabirds is reviewed
for 70 species found in five subarctic
oceanographic regions of the northeastern
North Pacific Ocean and Bering Sea. Species
inhabiting estuaries and sheltered bays are
not included. The diets of cormorants, marine
ducks, alcids, and marine raptors are best
known; less information is available for loons,
grebes, petrels, and gulls. Enough is known,
however, to broadly characterize the diet of
each species. Less than 7% of all species feed
on one type of prey, about 60% feed on two or
three types, and the rest feed on four or more
types. Only 12% of all species feed on eight
or more types of prey. Most seabirds (77%)
feed as secondary and tertiary carnivores.
Where overlap in diet exists, seabirds
partition resources through use of different
feeding methods, selection of different-sized
prey, and zonation of habitat. Species that
have specialized diets are probably more
susceptible than others to local environmental
catastrophes. Species whose feeding methods are
highly adapted for exploitation of resources
in polar and subpolar habitats are not adapted
for coping with oil pollution. Competition
between birds and man for marine resources can
sometimes benefit seabirds and at other times
harm them. More research is needed on seabird
feeding relations so that the ecological roles
played by marine birds can be defined and
placed in perspective. Such work should be
conducted at the community level, year-round,
and should be so conducted as to facilitate
comparison with biological oceanographic data.

The ecology, morphology, and much of the behavior of a seabird species are definable in terms of the food resources it exploits year-round and the spatial and temporal relations between food and breeding sites. This general point unifies such important reports as those by Kuroda (1954), Bédard (1969_a_), Ashmole and Ashmole (1967), Ashmole (1971), Spring (1971), and Sealy (1972). More concretely, information on trophic relations of seabirds is useful in several ways. In conjunction with biological oceanographic data, it can provide insight into geographic location, marine habitat, depth, time of day, and general method of food capture by seabirds. Collected over several years, it can provide a basis for understanding annual differences in seabird breeding phenology and success. Finally, supplemented with data on how much seabirds eat and excrete, it is necessary for an understanding of the energetic and ecological roles played by the birds in the functioning of marine ecosystems.

Several studies that describe trophic relations within seabird communities have helped to define the principals of community organization pertaining to the exploitation of available food resources and have given clues to food-chain pathways. Trophic relations have been described for breeding communities in the Barents Sea (Uspenski 1958; Belopol'skii 1961), in the tropical Pacific Ocean (Ashmole and Ashmole 1967; Ashmole 1968), in the North Sea (Pearson 1968), and in the Chukchi Sea (Swartz 1966). The last-named study pertained most directly to the geographic region discussed in this paper, but several other studies have provided sound information on segments of communities in the northeastern North Pacific and Bering Sea. These include the work on three species of auklets (_Aethia_, _Cyclorrhynchus_) in the Bering Sea (Bédard 1969_a_); investigations on cormorants and other fish predators in British Columbia by Munro (1941), Munro and Clemens (1931), and Robertson (1974); studies of murres in Bristol Bay by Ogi and Tsujita (1973); observations on several species near the Pribilof Islands by Preble and McAtee (1923); work on diving species off Oregon by Scott (1973); and studies of murrelets by Sealy (1975).

A review of available reports reveals three obvious gaps in the emphasis placed in seabird food studies. First, few studies have ever considered in detail the trophic relations of seabird communities during the winter or nonbreeding season. Partial exceptions are the works by Cottam (1939) and others on marine diving ducks, species that are seabirds only during the winter, and by several researchers (Munro and Clemens 1931; Munro 1941; Robertson 1974) on seabirds in British Columbia. Divoky (1976) studied diets of pack-ice gulls during the nonbreeding season, but those species are not included in the present analysis because they rarely are found south of the Bering Strait. Second, no study has considered the trophic relationships of an entire seabird community, i.e., not just breeding species but also nonbreeding species. In the rather broad communities considered here, 50-70% or more of the birds breed in another part of the world. To say that these nonbreeding species have no significant impact on resource exploitation or on organization and evolution among breeding members would be naive. Finally, few investigators have attempted to fit birds into an entire ecosystem, including lower trophic level origins as well as fish, marine mammals, and man.

The reasons for these gaps in study emphasis are readily apparent: the inconvenience of marine research during the winter when weather is stormy, the need for costly study platforms (boats), and the difficulties in organizing the specialized community of biologists required for such tasks. A less obvious but important reason is that oceanographers and fishery biologists have overlooked seabirds as important members of marine ecosystems.

Diets of Seabirds in Western North America

Relatively good information exists for most pelecaniformes of the region. A notable exception is the brown pelican _(Pelecanus occidentalis)_, an endangered species. This is unfortunate because dietary information is important for understanding the species' ecology. Observations in eastern North America (Palmer 1962) and Peru (Murphy 1936) indicated that their diet consisted of fish that occur at the surface. The larger cormorants are piscivorous, particularly on schooling fishes that occur at moderate to great depths (Table 1). The smaller cormorants feed more heavily on benthic fish and decapod crustaceans. Cormorants apparently feed only during daylight and then only for short periods because their wettable plumage loses its buoyancy. Thus they remain relatively close (50 km) to nesting and loafing areas.

Table 1. _Food of cormorants in different localities_ (x = major
prey, o = minor prey and * = incidental prey species)

-----------------------------------------------------------------------
Key:
A_Amphipod
B: Isopod
C: Decapod
D: _Clupea_
E: _Engraulis_
F: Salmonid
G: Argentinid
H: _Porichthys_
I: _Otophidium_
J: _Boreogadus_
K: _Microgadus_
L: _Gasterosteus_
M: _Sebastes_
N: Hexagrammid
O: Cottid
P: Agonid
Q: Embiotocid
R: _Chromis_
S: _Oxyjulis_
T: Stichacid
U: Pholid
V: Gobiid
W: _Ammodytes_
X: Pleuronectid
Y: Bothid

CRUSTACEAN
Location Diet A B C D E F G H I J K L M
-----------------------------------------------------------------------
Double-crested cormorant
_(Phalacrocorax auritus)_[16]
Alaska Peninsula (Palmer 1962) o o o x x x
SE Alaska (Bailey 1927) x
Mandarte Island (Robertson 1974) * * * * *
Vancouver Island (Munro and
Clemens 1931) x
Oregon (Palmer 1962) x * * x
Farallon Island (PRBO,
unpublished data) * *
Brandt's cormorant _(P.
penicillatus)_[17]
Vancouver Island (Robertson,
unpublished data) x
Vancouver Island (Munro and
Clemens 1931) x
Washington (Jewett et al. 1953)
Yaquina Head (Scott 1973) x o o
Farallon Island (PRBO,
unpublished data) * o * * x x x
San Diego (Hubbs
et al. 1970) *
Pelagic cormorant
_(P. pelagicus)_[18]
Cape Thompson (Swartz 1966) x x
Pribilof Island (Preble
and McAtee 1923) x
Alaska (Palmer 1962) x x x
SE Alaska (Heath 1915) x x
Mandarte Island (Robertson 1974) x
Vancouver Island
(Munro and Clemens 1921) x x x
Washington (Jewett et al. 1953) x x
Netarts, Oregon (Gabrielson and
Jewett 1940) * * x
Yaquina Head (Scott 1973) o o
Farallon Island (PRBO,
unpublished data) x x
Red-faced cormorant _(P. urile)_
Pribilof Islands (Preble and
McAtee 1923) x
-----------------------------------------------------------------------

-----------------------------------------------------------------------
CRUSTACEAN FISH
Location Diet N O P Q R S T U V W X Y
-----------------------------------------------------------------------
Double-crested cormorant
_(Phalacrocorax auritus)_[16]
Alaska Peninsula (Palmer 1962) o x
SE Alaska (Bailey 1927)
Mandarte Island (Robertson 1974) * o x x
Vancouver Island (Munro and Clemens 1931)
Oregon (Palmer 1962) * x * *
Farallon Island (PRBO, unpublished data) * x * * *
Brandt's cormorant _(P. penicillatus)_[17]
Vancouver Island (Robertson,
unpublished data) o x
Vancouver Island (Munro and Clemens 1931)
Washington (Jewett et al. 1953) x
Yaquina Head (Scott 1973) * o o o
Farallon Island (PRBO, unpublished data) * o * * *
San Diego (Hubbs et al. 1970) * o o * x
Pelagic cormorant _(P. pelagicus)_[18]
Cape Thompson (Swartz 1966) x x
Pribilof Island (Preble and McAtee 1923) x x
Alaska (Palmer 1962) x x x x x x
SE Alaska (Heath 1915) x
Mandarte Island (Robertson 1974) * * x x
Vancouver Island (Munro and Clemens 1921) x x x
Washington (Jewett et al. 1953) x x
Netarts, Oregon (Gabrielson and Jewett 1940) x
Yaquina Head (Scott 1973) x
Farallon Island (PRBO, unpublished data) x x
Red-faced cormorant _(P. urile)_
Pribilof Islands (Preble and McAtee 1923) x x x x x
-------------------------------------------------------------------------------

Table 2. _Food of marine ducks and geese (x = major prey, o =
minor prey, and * = incidental prey species_).[a]

Key:
A: Amphipods
B: Decapods
C: Barnacles
D: Mussels
E: Rock clams
F: Razor clams
G: Oysters, Scallops
H: Littorinids
I: Chitons

------------------------------------------------------------------------
|PLANTS
| |CRUSTACEANS
| | |MOLLUSCS
| | | |ECHINODERMS
Diet[19] | | | | |FISH
Location | |A|B|C|D|E|F|G|H|I| | |FISH EGGS
------------------------------------------------------------------------
=Geese= x
(_Branta_ spp.)
=Emperor goose= x
_(Philacte canagica)_
=Oldsquaw= o * * * * * * * o
_(Clangula hyemalis)_
=Harlequin duck= * x x o * * o o * *
_(Histrionicus histrionicus)_
=Steller's eider= o x * * * * o * * * *
_(Polysticta stelleri)_
=Common eider= * * x * o * o o * o *
_(Somateria mollissima)_
=King eider= * * o * x * o o * x *
_(S. spectabilis)_
=Spectacled eider= x * x o * * * *
_(S. fischeri)_
=White-winged scoter= * * * * o x * x o * * o o
_(Melanitta deglandi)_
=Surf scoter= o * * * x * * x o * * * o
_(M. perspicillata)_
=Black scoter= o * * o x * * x * * * *
_(M. nigra)_
=Red-breasted merganser= x
_(Mergus serrator)_
------------------------------------------------------------------------

Information on diets of marine ducks (Table 2) is more nearly complete than for most other seabirds. These birds fall into four groups with some overlap: species feeding on plants (_Branta, Philacte_, _Anas_-type, and _Somateria fischeri_); those feeding on benthic crustaceans (_Clangula hyemalis_, _Histrionicus histrionicus_, _Polysticta stelleri_, _S. mollissima_); those feeding on benthic molluscs (_Somateria_ spp. and _Melanitta_ spp.); and those feeding on fish (_Mergus serrator_, _Clangula hyemalis_, and _Melanitta deglandi_). A study by Perthon (1968), one of the few on a seabird's diet during most of a year, showed a seasonal change in diet for _S. mollissima_ in Norway. In general, waterfowl seem to specialize in their diets much more than other seabirds and, for that reason, are perhaps more restricted in their distributions. Some marine ducks are known to dive to considerable depths (reviewed by Kooyman 1974), but usually they occur in shallow waters where plants and sessile invertebrates are readily available.

The summer diet of the pigeon guillemot _(Cepphus columba)_ is the best known among seabirds in the region being considered here (Table 3). Only in the extreme southern part of its range (i.e., the California Channel Islands) is there no information available on its diet. The species feeds on organisms, mostly fish, from rocky habitat and apparently can dive to considerable depths (Follett and Ainley 1976). Because so much is known about guillemot diets during summer, a study of the winter diet would be valuable.

The diets of other alcids are known well enough to at least characterize them broadly. The larger species, murres, tufted and horned puffins (_Lunda cirrhata_, _Fratercula corniculata_), and the rhinoceros auklet _(Cerorhinca monocerata)_, feed heavily on fish, mainly species that school in midwater (Table 4). To a great degree, these birds are opportunistic, feeding rather heavily at times on cephalopods and crustaceans, particularly nektonic forms. Morphological differences between the two murre species suggest that thick-billed murres _(Uria lomvia)_ feed on benthic organisms much more than do common murres _(U. aalge)_, and that the latter species is more piscivorous (Spring 1971); however, field data on diets are barely adequate to confirm this. Ogi and Tsujita (1973) analyzed the stomach contents of murres drowned in salmon gill nets but did not separate the two species. For the present paper we considered them to be mostly _U. aalge_, since this species predominates in the region of the food study (Bartonek and Gibson 1972). Adult murres sometimes eat different items than they feed to their chicks (Spring 1971; Scott 1973). The smaller alcids, ancient and marbled murrelets--_Synthliboramphus antiquus_ and _Brachyramphus marmoratus_--(Table 5) and auklets (Table 6), feed on macrozooplankton: crustaceans, and fish and squid larvae. Little is known about the food or feeding ecology of Kittlitz's murrelet _(B. brevirostris)_. Its diet is probably similar to that of the other murrelets, especially the marbled murrelet, its allopatric congener, but the diets of the other murrelets differ somewhat (Bédard 1969_b_; Sealy 1975). The Kittlitz's murrelet's shorter bill suggests that it feeds more on invertebrates. Alcids feed in deep or shallow water, depending on food distribution. Some alcid species can be found at great distances from land, particularly in winter (Hamilton 1958; Scott et al. 1971).

Information on the diets of other seabirds in the region is fragmentary and sometimes rather anecdotal. A little is known about the feeding habits of loons (_Gavia_ spp.) and grebes (_Podiceps_ spp. and _Aechmophorus occidentalis_), especially off British Columbia (Table 7). The larger of these birds feed mainly on inshore fish, but as species become progressively smaller, there is a tendency toward eating crustaceans. Work by Madsen (1957) in Denmark, indicated that loons and grebes tend to take prey near or on the bottom. Much more information is available on these birds' diets at their freshwater breeding sites but this provides only partial insight into what they might eat in marine habitats.

Information is especially poor for albatrosses and petrels (order Procellariiformes) (Table 8). Yet, based on sheer numbers alone, members of this diverse group are easily among the most ecologically dominant of the region (Sanger 1972; Ainley 1977). The Laysan albatross _(Diomedea immutabilis)_ seems to be a squid specialist; the black-footed albatross _(D. nigripes)_, northern fulmar _(Fulmarus glacialis)_, scaled petrel _(Pterodroma inexpectata)_, and the fork-tailed and Leach's storm-petrels (_Oceanodroma furcata_ and _O. leucorhoa_) appear to be large, medium, small, and tiny versions, respectively, of surface-feeding generalists that eat whatever they can find, including live and dead fish, squid, coelenterates, crustaceans, and other organisms. The shearwaters (_Puffinus_ spp.) feed to an unknown degree on schooling fish, squid, and crustaceans that occur near the surface. For these very abundant shearwaters, that, unfortunately, is close to the extent of our knowledge both for the North Pacific, where they winter, and the South Pacific, where they breed. Most petrels remain in oceanic habitats, but shearwaters, particularly the sooty shearwater _(Puffinus griseus)_, and sometimes fulmars feed close to, if not within, the inshore neritic habitat. A much better understanding of the diets of this group is sorely needed.

Table 3. _Food of the pigeon guillemot_ (Cepphus columba) _in
different localities (x = major prey, o = minor prey, and * =
incidental prey species)_.

Key:
A: Amphipod
B: Isopod
C: Decapod
D: Petromyzontid
E: Chimaerid
F: Clupeid
G: Osmerid
H: Gadid
I: Gasterosteid
J: Scorpaenid
K: Cottid
L: Agonid
M: Embiotocid
N: Bathymasterid
O: Clinid
P: Cryptacanthodid
Q: Cebidichthyid
R: Stichaeid
S: Pholid
T: Ammondytid
U: Bothid
V: Pleuronectid

----------------------------------------------------------------------------
|CRUSTACEAN
| |OCTOPUS
Diet | | |FISH
Location |A|B|C| |D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V
----------------------------------------------------------------------------
Cape Thompson o o
(Swartz 1966)
Pribilof Island o o o
(Preble and McAttee 1923)
Mandarte Island o o * o x o o * o * o o o o o o
(Drent 1965; Koelink 1972)
Vancouver Island o o o
(Munro and Clemens 1931)
Olympic Peninsula o o o o
(Thoresen and Booth 1958)
Yaquina Head o o o o o
(Scott 1973)
Farallon Island o o * x x * o o o o
(Follett and Ainley 1976)
----------------------------------------------------------------------------

Knowledge on the food of gulls, shorebirds, and related species is surprisingly scanty in view of all that is known about their breeding biology and social behavior. Little is known about the marine food of phalaropes, but by inference from their association with storm-petrels, plankton-feeding whales, and convergence lines (Martin and Myers 1969), their tiny size, and their method of feeding (picking at minuscule items on the water surface), one can guess that they feed on zooplankton and detritus. Skuas _(Catharacta skua)_ and jaegers (_Stercorarius_ spp.) apparently eat what they can find at the surface, as well as whatever they can steal from gulls and terns. Almost all the literature on their feeding (Bent 1946) dwells on accounts of their stealing from other birds. That spectacular behavior would seem to be so energetically costly, though, that it is probably less important than we have been led to believe. Rather surprisingly, the question of what foods the gulls and terns eat in the eastern North Pacific is difficult to answer from the literature (Tables 9 and 10). Some information exists for five of the larger larids at isolated places, but little is known about food elsewhere in their respective ranges, and the diets of the seven smaller gulls and the terns are practically unknown. Studies on gull diets in the Atlantic region (e.g., Spaans 1971; Harris 1965) provide information on what to expect from the same species in the Pacific, but that information must be considered only in general terms because, the birds being somewhat opportunistic, their diets differ greatly from one locality to another (Ingolfsson 1967). A few observations are available for arctic terns _(Sterna paradisaea)_ in Alaska, but little information exists for other terns (Table 10). Bent (1921) noted that Aleutian terns _(S. aleutica)_ sometimes associate with arctic terns during feeding.

Finally, we must include raptors, particularly the peregrine _(Falco peregrinus)_ and bald eagle _(Haliaeetus leucocephalus)_, because they are important predators on the smaller seabirds (White et al. 1971, 1973). Peregrines have, in fact, been observed feeding on storm-petrels far at sea (Craddock and Carlson 1970).

Trophic Relations Within Seabird Communities

We have compared and summarized in general terms the food partitioning by species in five rather broad oceanographic regions and their subdivisions in the northeastern North Pacific and Bering Sea, based on the specific details on diets presented in Tables 1 through 10. The five broad regions, defined oceanographically by Dodimead et al. (1963) and Favorite et al. (1976) and modified by Sanger (1972), are shown in Fig. 1. The five oceanographic regions (domains) were divided further into inshore neritic, offshore neritic, and oceanic habitats (Sanger and King, this volume). We did not include estuarine habitats or sheltered bays in the analysis.

Table 4. _Food of murres and puffins in different
localities (x = major prey, o = minor prey, and * = incidental
prey species)._

KEY:

CRUSTACEAN
A - Euphausiid
B - Amphipod
C - Isopod
D - Decapod

E - POLYCHAETE

F - CEPHALOPOD

CRUSTACEAN POLYCHAETE CEPHALOPOD
LOCATION A B C D E F
--------
=Common murre= _(Uria aalge)_[20]
Cape Thompson o o o o o
(Swartz 1966)
Pribilof Islands x o o
(Preble and McAtee 1923)
E. Bering Sea x o
(Ogi and Tsujita 1973)
Forrester Island o o
(Heath 1915)
Vancouver Island o o
(Robertson, unpublished
data)
Olympic Peninsula
(Cody 1973)
Yaquina Head x o
(Scott 1973)
Farallon Islands x o
(PRBO, unpublished data)

=Thick-billed murre=
_(U. lomvia)_[21]
Cape Thompson o o o
(Swartz 1966)
Pribilof Islands x x
(Preble and McAtee 1923)
Hooker Island x o
(Demme 1934, _in_
Dement'ev et al. 1968)
NE Canada x o o o
(Tuck and Squires 1937)

=Tufted puffin=
_(Lunda cirrhata)_[22]
Cape Thompson *
(Swartz 1966)
Forrester Island
(Heath 1915)
Langara Island
(Sealy 1973_a_)
Washington
(Jewett et al. 1953)
Olympic Peninsula
(Cody 1973)
Farallon Island
(PRBO, unpublished data) x

=Horned puffin=
_(Fratercula corniculata)_
Cape Thompson o
(Swartz 1966)
Alaska
(Bent 1946)
Forrester Island
(Heath 1915)

=Rhinoceros auklet=
_(Cerorhinca monocerata)_
NW Pacific (Kozlova 1961; x
Komaki 1967)
Forrester Island
(Heath 1915)
Langara Island
(Sealy 1973_a_)
Destruction Island
(Richardson 1961)
Olympic Peninsula
(Cody 1973)
So. California (Linton x
1908; Grinnell 1899)
---------------------------------------------------------------

KEY:

FISH
G - Clupea
H - Sardinops
I - Engraulis
J - Salmo
K - Onchorhynchus
L - Hypomesus
M - Thaleichthys
N - Mallotus
O - Boreogadus
P - Microgadus
Q - Theragra
R - Lycodes
S - Gasterosteus
T - Sebaste
U - Triglops
V - Myoxocephalus
W - Cottid
X - Cymatogaster
Y - Embiotocid
Z - Chirolophis
AA - Stichaeid
BB - Ammodytes
CC - Pleuronectid
DD - Liparid

FISH A B C D
LOCATION G H I J K L M N O P Q R S T U V W X Y Z A B C D
--------
=Common murre= _(Uria aalge)_[20]
Cape Thompson x o o o x
(Swartz 1966)
Pribilof Islands o
(Preble and McAtee 1923)
E. Bering Sea x x x
(Ogi and Tsujita 1973)
Forrester Island x
(Heath 1915)
Vancouver Island x o
(Robertson, unpublished
data) x x o o
Olympic Peninsula
(Cody 1973) x x o x o o o
Yaquina Head
(Scott 1973) x o o * x o o
Farallon Islands
(PRBO, unpublished data)

=Thick-billed murre=
_(U. lomvia)_[21] x o o o o o x o
Cape Thompson
(Swartz 1966)
Pribilof Islands
(Preble and McAtee 1923)
Hooker Island
(Demme 1934, _in_
Dement'ev et al. 1968) o x * x * o x o o o
NE Canada
(Tuck and Squires 1937)

=Tufted puffin= x
_(Lunda cirrhata)_[22] *
Cape Thompson
(Swartz 1966) x
Forrester Island
(Heath 1915) x
Langara Island x
(Sealy 1973_a_) x x x x
Washington o
(Jewett et al. 1953) x o x
Olympic Peninsula x
(Cody 1973) x o
Farallon Island
(PRBO, unpublished data)

=Horned puffin= x o
_(Fratercula corniculata)_ o x
Cape Thompson
(Swartz 1966)
Alaska
(Bent 1946) x
Forrester Island
(Heath 1915)

=Rhinoceros auklet=
_(Cerorhinca monocerata)_ x o x x
NW Pacific (Kozlova 1961;
Komaki 1967) x
Forrester Island
(Heath 1915) x
Langara Island
(Sealy 1973_a_) o x
Destruction Island o
(Richardson 1961) x x o
Olympic Peninsula
(Cody 1973) x
So. California (Linton
1908; Grinnell 1899)
-----------------------------------------------------------------------------

Table 5. _Food of ancient and marbled murrelets (x = major prey,
o = minor prey, and * = incidental prey species)._

Column Headings:

CRUSTACEAN
A - Euphausiid
B - Thysanoessa
C - Euphausia
D - Mysid
E - Acanthomysis
F - Amphipod
G - Gammarid
H - Carid shrimp
I - Decapod
J - Larvae

CRUSTACEAN

Location DIET A B C D E F G H I J
------------------------------------------------------------------------------
=Ancient murrelet= _(Synthliboramphus antiquus)_[23]

Commander Islands (Dement'ev et al. 1968) x x
Amchitka Island (White et al. 1971, 1973) x x x x
Langara Island (Sealy 1975) x x x * * *

=Marbled murrelet= _(Brachyramphus marmoratus)_[24]

SE Alaska (Grinnell 1897)
Langara Island (Sealy 1975) x x *
Vancouver Island (Munro and Clemens 1931) x
Olympic Peninsula (Cody 1973)

Column Headings:

SQUID
K - Larvae

FISH
L - Engraulis
M - Osmerid
N - Scorpaenid
O - Cymatogaster
P - Stichaeid
Q - Ammodytes
R - Larvae

SQUID FISH

Location DIET K L M N O P Q R
-----------------------------------------------------------------------------
=Ancient murrelet= _(Synthliboramphus antiquus)_[23]

Commander Islands (Dement'ev et al. 1968)
Amchitka Island (White et al. 1971, 1973) x
Langara Island (Sealy 1975) o o x

=Marbled murrelet= _(Brachyramphus marmoratus)_[24]

SE Alaska (Grinnell 1897) o
Langara Island (Sealy 1975) * * * x *
Vancouver Island (Munro and Clemens 1931) x x
Olympic Peninsula (Cody 1973) x x

Table 6. _Diets of auklets in different localities (x = major
prey, o = minor prey, and * = incidental prey species)._

Table Headings

CRUSTACEAN
A - Euphausiid
B - Thysanoessa
C - Mysid
D - Stylomysis
E - Amphipod
F - Parathemisto
G - Phronema
H - Gammarid
I - Copepod
J - Calanus
K - Carid shrimp

L - POLYCHAETE

SQUID
M - Larvae

FISH
N - Cottid
O - Larvae

Location Diet A B C D E F G H I J K L M N O

=Cassin's auklet=
_(Ptychoramphus aleuticus)_
Forrester Island (Heath 1915) x x x
Olympic Peninsula (Cody 1973) x x
Farallon Islands (Manuwal 1974) x x x x x o x

=Parakeet auklet=
_(Cyclorrhynchus psittaculus)_
Chukhotsk Peninsula (Portenko 1934,
_in_ Dement'ev et al. 1968) x x x x x
Aleutian Islands (Bent 1946) x
St. Lawrence Island (Bédard 1969_a_) x x o x x o o * o o o

=Crested auklet=
_(Aethia cristatella)_[25]
W. Bering Sea (Portenko 1934,
_in_ Dement'ev et al. 1968) x x
Commander Islands (Stejneger 1885) x
Amchitka (White et al. 1973) x x x x x
St. Lawrence Island. (Bédard 1969_a_) x x x o o x x *
Pribilof Islands (Preble and McAtee 1923) x x

=Least auklet= _(A. pusilla)_
Commander Islands (Stejneger 1885) x
Aleutian Islands (Bent 1946) x
St. Lawrence Island (Bédard 1969_a_) o o * o o o x x x

=Whiskered auklet= _(A. pygmaea)_
Commander Islands (Stejneger 1885) x x *

Table 7. _Diets of loons and grebes in different localities (x =
major prey, o = minor prey, and * = incidental prey species)._

Table Headings:

CRUSTACEANS
A - Euphausid
B - Amphipod
C - Mysid
D - Decapod

E - POLYCHAETE

FISH
F - Anguilla
G - Clapea
H - Sardinops
I - Salmo
J - Thaleichthys
K - Atherinops
Location A B C D E F G H I J K

=Common loon= _(Gavia immer)_
Alaska (Palmer 1962) * * o o
Vancouver Island (Munro and Clemens 1931) x
Denmark (Madsen 1957) *

=Yellow-billed loon= _(G. adamsii)_[26]
Alaska (Cottam and Knappen 1939) * *
Alaska (Bailey 1922)

=Arctic loon= _(G. arctica)_[27]
Vancouver Island (Palmer 1962) x
Vancouver Island (Robertson, unpublished data) x
California (Palmer 1962)
Denmark (Madsen 1957) * o

=Red-throated loon= _(G. stellata)_[28]
Oregon (Palmer 1962)
No. Atlantic (Palmer 1962)
Denmark (Madsen 1957) * o

=Western grebe= _(Aechmophorus occidentalis)_
Vancouver Island (Munro 1941) o * x
Vancouver Island (Robertson, unpublished data) x
Puget Sound (Phillips and Carter 1957) x
Washington (Chatwin 1956) * x
California (Palmer 1962) o * x x

=Red-necked grebe= _(Podiceps grisegena)_
Pribilof Islands (Preble and McAtee 1923) o
Vancouver Island (Wetmore 1924)
Vancouver Island (Munro 1941) x o
E. No. America (Wetmore 1924) o * o

=Horned grebe= _(P. auritus)_[29]
Pribilof Islands (Preble and McAtee 1923) x o
W. No. America (Wetmore 1924) x x *
Vancouver Island (Munro 1941) x x
Denmark (Madsen 1957) o o o

=Eared grebe= _(P. nigricollis)_[30]
W. No. America (Wetmore 1924) * x *
Vancouver Island (Munro 1941) x x o
Denmark (Madsen 1957) x *

Table Headings:

FISH
L - Zoarchid
M - Gadid
N - Fundulus
O - Gasterosteus
P - Sebastes
Q - Cattid
R - Cymatogaster
S - Stichaeid
T - Ammodytes
U - Gobiid
Location L M N O P Q R S T U

=Common loon= _(Gavia immer)_
Alaska (Palmer 1962) o o o
Vancouver Island (Munro and Clemens 1931)
Denmark (Madsen 1957) o x * o

=Yellow-billed loon= _(G. adamsii)_[26]
Alaska (Cottam and Knappen 1939) o x
Alaska (Bailey 1922) x

=Arctic loon= _(G. arctica)_[27]
Vancouver Island (Palmer 1962)
Vancouver Island (Robertson, unpublished data)
California (Palmer 1962) x
Denmark (Madsen 1957) * x x * x *

=Red-throated loon= _(G. stellata)_[28]
Oregon (Palmer 1962) x
No. Atlantic (Palmer 1962) x x o
Denmark (Madsen 1957) * x o * * o

=Western grebe= _(Aechmophorus occidentalis)_
Vancouver Island (Munro 1941) x
Vancouver Island (Robertson, unpublished data) x
Puget Sound (Phillips and Carter 1957) * o o o
Washington (Chatwin 1956)
California (Palmer 1962) x *

=Red-necked grebe= _(Podiceps grisegena)_
Pribilof Islands (Preble and McAtee 1923)
Vancouver Island (Wetmore 1924) x
Vancouver Island (Munro 1941) x
E. No. America (Wetmore 1924) o x

=Horned grebe= _(P. auritus)_[29]
Pribilof Islands (Preble and McAtee 1923)
W. No. America (Wetmore 1924) o o
Vancouver Island (Munro 1941) o o *
Denmark (Madsen 1957) o

=Eared grebe= _(P. nigricollis)_[30]
W. No. America (Wetmore 1924) o
Vancouver Island (Munro 1941)
Denmark (Madsen 1957) o

Table 8. _Diets of albatrosses and petrels in different
localities (x = major prey, o = minor prey, and * = incidental prey
species)._

Key:
CRUSTACEAN
A: Euphausiid
B: Amphipod
C: Copepod
D: Decapod
E: Larvae
F: Barnacle

FISH
G: "Fish"
H: _Engraulis_
I: Myctophid
J: _Sebastes_
K: _Ammodytes_
L: Carrion, fish offal
M: Fish eggs

-----------------------------------------------------------------------------
|CRUSTACEAN
| |COELENTERATE
| | |ECHINODERM
| | | |CEPHALOPOD
Location Diet |A|B|C|D|E|F| | | |
---------------------------------------------------------------------
=Black-footed albatross= _(Diomedea nigripes)_
No. Pacific (Palmer 1962) x
Aleutian Islands (Cottam and Knappen 1939) o x o
California (Miller 1936, 1940) o o x
=Laysan albatross= _(D. immutabilis)_
No. Pacific (Palmer 1962; Bartsch 1922;
Fisher 1904) x
=Northern fulmar= _(Fulmarus glacialis)_
Pribilof Islands (Preble and McAtee 1923) o x
Alaska (Gabrielson and Lincoln 1959) x x
Oregon (Gabrielson and Jewett 1940) x
No. Atlantic (Hartley and Fisher 1936;
Einarsson 1945; Fisher 1952) x
=Flesh-footed shearwater= _(Puffinus carneipes)_
Australia (Oliver 1955; Serventy et al. 1971) x x
=Pink-footed shearwater= _(P. creatopus)_
California (Murphy 1936; Ainley,
personal observation) x
E. Pacific (Cottam and Knappen 1939) x
=Buller's shearwater= _(P. bulleri)_
SW Pacific (Falla 1934; Serventy et al. 1971) x x
Peru (Murphy 1936) x
=Sooty shearwater= _(P. griseus)_
Aleutian Islands (Sanger, personal
observation) x x
British Columbia (Martin 1942; Sealy 1973_a_) x
Oregon (Gabrielson and Jewett 1940) x
California (Ainley, personal observation) x
Peru (Murphy 1936) x x
SW Pacific (Oliver 1955; Serventy et al. 1971) x x
=Short-tailed shearwater= _(P. tenuirostris)_
Bristol Bay (Bartonek, personal communication) x
Alaska (Cottam and Knappen 1939) x x x
No. Pacific (Palmer 1962; Kuroda 1955) x x
Australia (Serventy et al. 1971) x x
Bass Strait (Sheard 1953) x
=Mottled petrel= _(Pterodroma inexpectata)_
Pacific Ocean (Imber 1973)
E. No. Pacific (Kuroda 1955)
=Fork-tailed storm-petrel=_(Oceanodroma furcata)_
Pribilof Islands (Preble and McAtee 1923)
SE Alaska (Heath 1915) x
British Columbia (Martin 1942)
California (Ainley, personal observation)
=Leach's storm-petrel= _(O. leucorhoa)_
SE Alaska (Heath 1915) x
California (PRBO, unpublished data) x x x
So. California (Palmer 1962) x
No. Atlantic[31] (Palmer 1962) x x x
---------------------------------------------------------------------

----------------------------------------------------------------
|FISH
Location Diet|G|H|I|J|K|L|M
----------------------------------------------------------------
=Black-footed albatross= _(Diomedea nigripes)_
No. Pacific (Palmer 1962) x x
Aleutian Islands (Cottam and Knappen 1939) x x
California (Miller 1936, 1940) x x x
=Laysan albatross= _(D. immutabilis)_
No. Pacific (Palmer 1962; Bartsch 1922;
Fisher 1904)
=Northern fulmar= _(Fulmarus glacialis)_
Pribilof Islands (Preble and McAtee 1923)
Alaska (Gabrielson and Lincoln 1959) x
Oregon (Gabrielson and Jewett 1940)
No. Atlantic (Hartley and Fisher 1936;
Einarsson 1945; Fisher 1952) x
=Flesh-footed shearwater= _(Puffinus carneipes)_
Australia (Oliver 1955; Serventy et al. 1971) x
=Pink-footed shearwater= _(P. creatopus)_
California (Murphy 1936; Ainley,
personal observation) x
E. Pacific (Cottam and Knappen 1939) x
=Buller's shearwater= _(P. bulleri)_
SW Pacific (Falla 1934; Serventy et al. 1971) x
Peru (Murphy 1936)
=Sooty shearwater= _(P. griseus)_
Aleutian Islands (Sanger, personal
observation) x
British Columbia (Martin 1942; Sealy 1973_a_) x x
Oregon (Gabrielson and Jewett 1940)
California (Ainley, personal observation) x
Peru (Murphy 1936) x
SW Pacific (Oliver 1955; Serventy et al. 1971) x
=Short-tailed shearwater= _(P. tenuirostris)_
Bristol Bay (Bartonek, personal communication)
Alaska (Cottam and Knappen 1939) o
No. Pacific (Palmer 1962; Kuroda 1955) x
Australia (Serventy et al. 1971) x
Bass Strait (Sheard 1953)
=Mottled petrel= _(Pterodroma inexpectata)_
Pacific Ocean (Imber 1973) x
E. No. Pacific (Kuroda 1955) x
=Fork-tailed storm-petrel= _(Oceanodroma furcata)_
Pribilof Islands (Preble and McAtee 1923) x
SE Alaska (Heath 1915)
British Columbia (Martin 1942) x
California (Ainley, personal observation) x
=Leach's storm-petrel= _(O. leucorhoa)_
SE Alaska (Heath 1915)
California (PRBO, unpublished data) x x
So. California (Palmer 1962) x
No. Atlantic[31] (Palmer 1962) x x
----------------------------------------------------------------

Table 9. _Diets of gulls in different localities (x = major prey,
o = minor prey, and * = incidental prey species)._

Key:
CRUSTACEAN
A: Euphausiid
B: Barnacle
C: Decapod

MOLLUSC
D: Shell fish
E: Cephalopod

FISH
F: "Fish"
G: _Clupea_
H: _Engraulis_
I: _Osmerus_
J: _Porichihys_
K: _Otaphidium_
L: _Mallotus_
M: _Borrogadus_
N: _Microgadus_
O: _Gadus_
P: _Lycodes_
Q: _Sebastes_
R: _Myxocephalus_
S: _Genyonemus_
T: Embiotocid
U: _Ammodytes_

BIRD
V: Eggs
X: Chicks
Y: Adults

|CRUSTACEAN
| |POLYCHAETE
| | |MOLLUSC
| | | |ECHINODERM
| | | | |COELENTERATE
| | | | | |FISH
Diet | | | | | |
Location |A|B|C| |D|E| | |F|G|H|I|
---------------------------------------------------------------------------
=Glaucous gull= _(Larus hyperboreus)_
St. Lawrence Island (Fay and Cade 1959)
Chukchi Sea (Swartz 1966) x x x
Pribilof Islands (Preble and McAtee 1923) x x x x
Vancouver Island (Munro and Clemens 1931) x
=Glaucous-winged gull= _(L. glaucescens)_[32]
Pribilof Islands (Preble and McAtee 1923) x x x
Alaska (Bent 1921)
No. Pacific (Sanger 1973) x * *
Mandarte Island (Ward 1973) x x x
Vancouver Island (Munro and Clemens 1931; x x
Robertson, unpublished data)
=Western gull= _(L. occidentalis)_[33]
Farallon Islands (PRBO, unpublished data) x x o * x * * x
=Herring gull= _(L. argentatus)_
No. Atlantic (Zelikman 1961) x
E. No. America (Bent 1946; Ainley, x x x x x
personal observation)
Vancouver Island (Munro and Clemens 1931) x x
=Mew gull= _(L. canus)_
Alaska (Bent 1921) x
Vancouver Island (Munro and Clemens 1931) x x
=Heermann's gull= _(L. heermanni)_
California (Bent 1921) x x x
=Bonaparte's gull= _(L. philadelphia)_
E. No. America (Bent 1921) x x x
=Black-legged kittiwake= _(Rissa tridactyla)_[34]
Chukchi Sea (Swartz 1966) o * o
Pribilof Islands (Preble and McAtee 1923) o x
Alaska (Bent 1921) x
Cook Inlet[35] (Snarski, personal o o o
communication)
No. Atlantic (Hartley and Fisher x
1936; Zelikman 1961)
=Red-legged kittiwake= _(R. breuirostris)_
Pribilof Islands (Preble and McAtee 1923) x x x
=Sabine's gull= _(Xenia sabini)_
Pt. Barrow (Banner 1954) x
---------------------------------------------------------------------------
Location Diet |J|K|L|M|N|O|P|Q|R|S|T|U|
-----------------------------------------------------------------------------
=Glaucous gull= _(Larus hyperboreus)_
St. Lawrence Island (Fay and Cade 1959)
Chukchi Sea (Swartz 1966) x x
Pribilof Islands (Preble and McAtee 1923)
Vancouver Island (Munro and Clemens 1931)
=Glaucous-winged gull= _(L. glaucescens)_[32]
Pribilof Islands (Preble and McAtee 1923)
Alaska (Bent 1921)
No. Pacific (Sanger 1973)
Mandarte Island (Ward 1973) x
Vancouver Island (Munro and Clemens 1931;
Robertson, unpublished data)
=Western gull= _(L. occidentalis)_[33]
Farallon Islands (PRBO, unpublished data) x o o o x o o
=Herring gull= _(L. argentatus)_
No. Atlantic (Zelikman 1961)
E. No. America (Bent 1946; Ainley,
personal observation)
Vancouver Island (Munro and Clemens 1931)
=Mew gull= _(L. canus)_
Alaska (Bent 1921) x
Vancouver Island (Munro and Clemens 1931)
=Heermann's gull= _(L. heermanni)_
California (Bent 1921)
=Bonaparte's gull= _(L. philadelphia)_
E. No. America (Bent 1921)
=Black-legged kittiwake= _(Rissa tridactyla)_[34]
Chukchi Sea (Swartz 1966) o x o o x
Pribilof Islands (Preble and McAtee 1923)
Alaska (Bent 1921)
Cook Inlet[35] (Snarski, personal x o x
communication)
No. Atlantic (Hartley and Fisher
1936; Zelikman 1961)
=Red-legged kittiwake= _(R. breuirostris)_
Pribilof Islands (Preble and McAtee 1923)
=Sabine's gull= _(Xenia sabini)_
Pt. Barrow (Banner 1954)
-----------------------------------------------------------------------------
Diet |CARRION-OFFAL
| |BIRD
| | |FISH EGGS
Location | |V|X|Y|
----------------------------------------------------------------------
=Glaucous gull= _(Larus hyperboreus)_
St. Lawrence Island (Fay and Cade 1959) x x x
Chukchi Sea (Swartz 1966) x x
Pribilof Islands (Preble and McAtee 1923) x
Vancouver Island (Munro and Clemens 1931) x
=Glaucous-winged gull= _(L. glaucescens)_[32]
Pribilof Islands (Preble and McAtee 1923) x x x x
Alaska (Bent 1921) x
No. Pacific (Sanger 1973)
Mandarte Island (Ward 1973) x
Vancouver Island (Munro and Clemens 1931; x
Robertson, unpublished data)
=Western gull= _(L. occidentalis)_[33]
Farallon Islands (PRBO, unpublished data) x o o o
=Herring gull= _(L. argentatus)_
No. Atlantic (Zelikman 1961)
E. No. America (Bent 1946; Ainley, x * o x
personal observation)
Vancouver Island (Munro and Clemens 1931) x
=Mew gull= _(L. canus)_
Alaska (Bent 1921) x x
Vancouver Island (Munro and Clemens 1931) x
=Heermann's gull= _(L. heermanni)_
California (Bent 1921) x
=Bonaparte's gull= _(L. philadelphia)_
E. No. America (Bent 1921)
=Black-legged kittiwake= _(Rissa tridactyla)_[34]
Chukchi Sea (Swartz 1966)
Pribilof Islands (Preble and McAtee 1923) o
Alaska (Bent 1921) o
Cook Inlet[35] (Snarski, personal
communication)
No. Atlantic (Hartley and Fisher
1936; Zelikman 1961)
=Red-legged kittiwake= _(R. breuirostris)_
Pribilof Islands (Preble and McAtee 1923)
=Sabine's gull= _(Xenia sabini)_
Pt. Barrow (Banner 1954)
----------------------------------------------------------------------

=Table 10=. _Diets of terns in different localities (x = major prey
species)._

------------------------------------------------------------------------
CRUSTACEAN FISH
------------------------------------------------------------------------
|"Crustacean"|_Mallotus_
| |Euphausiid| |Cottid
Diet | | |Amphipod| | |_Ammodytes_
Location | | | | | | larvae
------------------------------------------------------------------------
=Arctic tern= _(Sterna paradisaea)_
Pribilof Islands (Preble and McAtee 1923) x x
Alaska (Bent 1921) x x x
No. Atlantic (Hartley and Fisher 1936) x
=Common tern= _(S. hirundo)_
E. No. America (Bent 1921) x x
------------------------------------------------------------------------

The oceanic habitat includes waters of the photic zone overlying the deep ocean and continental slopes beyond the continental or insular shelves. The Bering Sea and central subarctic domains are largely made up of oceanic habitat. The other three domains include both inshore and offshore neritic as well as some oceanic habitat. The boundary between the inshore and offshore neritic has yet to be defined in terms of bird life, but it lies at that line beyond which the bottom is too deep for a diving bird to exploit. A depth contour thus defines the boundary. In the antarctic South Pacific, emperor penguins _(Aptenodytes fosteri)_ dive to depths of 275 m, but so far as is known, no comparable bird exists in the North Pacific. Some marine ducks and loons reportedly dive to 50-60 m (Kooyman 1974). The inshore-offshore neritic boundary for seabirds may lie near the 70-m depth contour.

Food resource partitioning by seabirds in the five oceanographic domains are shown in Tables 11-15. Within each domain, the common and usual members of the seabird community are listed, and the major and minor categories in each of their diets are shown (on the basis of available literature, Tables 1-10). The categories are grouped further, and rather tenuously, according to the trophic level at which a bird is presumably feeding: I = herbivore, II = secondary carnivore, III = tertiary carnivore, IV = final carnivore, and Sc = scavengers (carnivorous) feeding at many levels. Birds at level I feed on large algae and seed plants and are not directly part of the same food webs involving other species. These food webs originate with phytoplankton (Fig. 2). So far as is known, no bird feeds on phytoplankton and few, if any, feed on microzooplankton; hence birds do not generally feed as primary carnivores. An exception at times might be the least auklet _(Aethia pusilla)_ when it feeds on small copepods (see Bédard 1969_b_).

The above groupings are "tenuous" because prey in each category may represent more than one trophic level, and a single prey species could occur at one level one day or place and at another level the next day or place, depending upon what it happened to be eating. This is shown in Fig. 2, where the parakeet auklet _(Cyclorrhynchus psittaculus)_ can occur in the food web at different levels, depending both on the prey it is eating and on what its prey is eating. Even without this complication, many seabirds feed at more than one level in the food web. For instance, murres eating euphausiids would be feeding at a different level than murres feeding on larger fish. It might be "safer" to regard prey organisms in level II as macrozooplankton, prey organisms in level III as micronekton, and prey organisms (seabirds themselves) in level IV as macronekton (after Sverdrup et al. 1942).

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.)

-----------------------------------------------------------------------------
Habitat, bird trophic levels (I-IV. Sc), and food categories
-----------------------------------------------------------------------------
Oceanic and offshore neritic Inshore neritic Inshore neritic
-----------------------------------------------------------------------------
Key:
II II III
A. Crustacean J. Crustacean, midwater R. Fish, midwater
B. Polychaete K. Crustacean, benthic S. Fish, benthic
C. Coelenterate L. Coelenterate T. Cephalopod
D. Fish/squid eggs & larvae M. Echinoderm IV. U. Birds
III N. Mollusc Sc. V. Carrion/offal/
E. Fish Q. Fish/squid eggs & larvae detritus
F. Cephalopod
IV G. Birds
Sc H. Carrion/offal/detritus
I I. Plant

Seabirds | A B C D| E F G H I| J K L |M N Q |R S T |U V |
----------------------------------------------------------------------------|
_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.)

Bird trophic levels and food categories

II III IV Sc
---------------------------------------------------------------------------
Fish/Squid eggs & Larvae | Fish
Coelenterate | | | Cephalopod
Polychaete | | | | | Birds
Crustacean | | | | | | | Carrion/offal
Seabirds | | | | | | | | | /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.)

----------------------------------------------------------------------------
Habitat, bird trophic levels (I-IV. Sc), and food categories

Key:
Oceanic and offshore neritic
II
A: Crustacean
B: Polychaete
C: Coelenterate
D: Fish/squid eggs & larvae

III
E: Fish
F: Cephalopod

IV
G: Birds

Sc
H: Carrion/offal/detritus

I
I: Plant

Inshore neritic
II
J: Crustacean, midwater
K: Crustacean, benthic
L: Coelenterate
M: Echinoderm IV:
N: Mollusc Sc:
Q: Fish/squid eggs & larvae

III
R: Fish, midwater
S: Fish, benthic
T: Cephalopod

IV
U: Birds

Sc
V: Carrion/offal/detritus

Seabirds A B C D E F G H I J K L M N Q R S T U V
----------------------------------------------------------------------------
_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.)

--------------------------------------------------------------------
Bird trophic levels and food categories
---------------------------------------
II III IV Sc
-------------- ------- --- ------------
|Crustacean
| |Polychaete
| | |Coelenterate
| | | |Fish/squid eggs & larvae
| | | | |Fish
| | | | | |Cephalopod
| | | | | | |Birds
Seabirds | | | | | | | |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).

Table 15. _Use of food resources by seabirds in the North
American coastal 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.)

-----------------------------------------------------------------
Habitat, bird trophic levels (I-IV, Sc), and food categories
-----------------------------------------------------------------
Key:
Oceanic and offshore neritic
II
A: Crustacean
B: Polychaete
C: Coelenterate
D: Fish-squid eggs & larvae

III
E: Fish
F: Cephalopod

IV
G: Birds

Sc
H: Carrion/offal/detritus

I
I: Plant

Inshore neritic
II
J: Crustacean, midwater
K: Crustacean, benthic
L: Coelenterate
M: Echinoderm
N: Mollusc
O: Fish/squid eggs & larvae

III
P: Fish, midwater
Q: Fish, benthic
R: Cephalopod

IV
S: Birds

Sc
T: Carrion/offal/detritus

Seabirds A B C D E F G H I J K L M N O P Q R S T
---------------------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
_Gavia immer_ * x x
_G. adamsii_ * o x
_G. arctica_ o x
_G. stellata_ o x
_Podiceps grisegena_ o x o
_P. nigricollis_ x o
_P. auritus_ x x o
_Aechmophorus occidentalis_ o x x
_Diomedea nigripes_ x o o o x x x
_Fulmarus glacialis_ x o x o x x x
_Puffinus creatopus_ o x x
_P. carneipes_ o x x
_P. bulleri_ x x x
_P. griseus_ x x x o o o
_P. tenuirostris_ x o x o o o
_Oceanodroma furcata_ x o o o x x x
_Pelecanus occidentalis_ x
_Phalacrocorax auritus_ o x o
_P. penicillatus_ o x
_P. pelagicus_ x x
_Branta bernicla_ x
_Clangula hyemalis_ o x o o
_Histrionicus histrionicus_ o x o
_Melanitta deglandi_ x o o
_M. perspicillata_ o x o
_M. nigra_ * o o x
_Mergus serrator_ * x x
_Haliaeetus leucocephalus_ x x x
_Falco peregrinus_ x
_Phalaropus fulicarius_ x x o x x o
_Lobipes lobatus_ x x o x x o
_Stercorarius_ spp. o x x ? x x x o 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 x x x x
_L. occidentalis_ x x x x o x o o o * * x x o x
_L. argentatus_ o o o o o x o o o o o x o x
_L. heermanni_ x x x
_L. canus_ x o o o x x x
_L. philadelphia_ x x o
_Rissa tridactyla_ x x x o
_Xema sabini_ x x o o
_Sterna paradisaea_ x x o o
_S. hirundo_ o x
_Uria aalge_ x o x x o x o
_U. lomvia_ x o x x o x o x
_Lunda cirrhata_ ? x x
_Fratercula corniculata_ * x x
_Cerorhinca monocerata_ x x
_Cepphus columba_ o x o
_Brachyramphus marmoratus_ x o x
_B. brevirostris_ x o
_Synthliboramphus antiquus_ x x o
_Ptychoramphus aleuticus_ x x
---------------------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

Table 16. _Number of seabirds of different oceanographic regions
having different numbers of categories of food in their diets._