Table 5.Food of ancient and marbled murrelets (x = major prey, o = minor prey, and * = incidental prey species).LocationDIETCRUSTACEANSQUIDFISHEuphausiidThysanoessaEuphausiaMysidAcanthomysisAmphipodGammaridCarid shrimpDecapodLarvaeLarvaeEngraulisOsmeridScorpaenidCymatogasterStichaeidAmmodytesLarvaeAncient murrelet(Synthliboramphus antiquus)[23]Commander Islands (Dement'ev et al. 1968)xxAmchitka Island (White et al. 1971, 1973)xxxxxLangara Island (Sealy 1975)xxx***ooxMarbled murrelet(Brachyramphus marmoratus)[24]SE Alaska (Grinnell 1897)oLangara Island (Sealy 1975)xx****x*Vancouver Island (Munro and Clemens 1931)xxxOlympic Peninsula (Cody 1973)xx
Table 6.Diets of auklets in different localities (x = major prey, o = minor prey, and * = incidental prey species).LocationDietCRUSTACEANPOLYCHAETESQUIDFISHEuphausiidThysanoessaMysidStylomysisAmphipodParathemistoPhronemaGammaridCopepodCalanusCarid shrimpLarvaeCottidLarvaeCassin's auklet(Ptychoramphus aleuticus)Forrester Island (Heath 1915)xxxOlympic Peninsula (Cody 1973)xxFarallon Islands (Manuwal 1974)xxxxxoxParakeet auklet(Cyclorrhynchus psittaculus)Chukhotsk Peninsula (Portenko 1934,inDement'ev et al. 1968)xxx xxAleutian Islands (Bent 1946)xSt. Lawrence Island (Bédard 1969a)xxoxxoo*oooCrested auklet(Aethia cristatella)[25]W. Bering Sea (Portenko 1934,inDement'ev et al. 1968)xxCommander Islands (Stejneger 1885)xAmchitka (White et al. 1973)xxxxxSt. Lawrence Island. (Bédard 1969a)xxxo oxx*Pribilof Islands (Preble and McAtee 1923)xxLeast auklet(A. pusilla)Commander Islands (Stejneger 1885)xAleutian Islands (Bent 1946)xSt. Lawrence Island (Bédard 1969a)oo*oooxxxWhiskered auklet(A. pygmaea)Commander Islands (Stejneger 1885)xx*
Table 7.Diets of loons and grebes in different localities (x = major prey, o = minor prey, and * = incidental prey species).LocationDietCRUSTACEANSPOLYCHAETEFISHEuphausidAmphipodMysidDecapodAnguillaClapeaSardinopsSalmoThaleichthysAtherinopsZoarchidGadidFundulusGasterosteusSebastesCattidCymatogasterStichaeidAmmodytesGobiidCommon loon(Gavia immer)Alaska (Palmer 1962)**oooooVancouver Island (Munro and Clemens 1931)xDenmark (Madsen 1957)*ox*oYellow-billed loon(G. adamsii)[26]Alaska (Cottam and Knappen 1939)**oxAlaska (Bailey 1922)xArctic loon(G. arctica)[27]Vancouver Island (Palmer 1962)xVancouver Island (Robertson, unpublished data)xCalifornia (Palmer 1962)xDenmark (Madsen 1957)*o*xx*x*Red-throated loon(G. stellata)[28]Oregon (Palmer 1962)xNo. Atlantic (Palmer 1962)xxoDenmark (Madsen 1957)*o*xo**oWestern grebe(Aechmophorus occidentalis)Vancouver Island (Munro 1941)o*xxVancouver Island (Robertson, unpublished data)xxPuget Sound (Phillips and Carter 1957)x*oooWashington (Chatwin 1956)*xCalifornia (Palmer 1962)o*xxx*Red-necked grebe(Podiceps grisegena)Pribilof Islands (Preble and McAtee 1923)oVancouver Island (Wetmore 1924)xVancouver Island (Munro 1941)xoxE. No. America (Wetmore 1924)o*ooxHorned grebe(P. auritus)[29]Pribilof Islands (Preble and McAtee 1923)xoW. No. America (Wetmore 1924)xx*ooVancouver Island (Munro 1941)xxoo*Denmark (Madsen 1957)ooooEared grebe(P. nigricollis)[30]W. No. America (Wetmore 1924)*x*oVancouver Island (Munro 1941)xxoDenmark (Madsen 1957)x*o
Table 8.Diets of albatrosses and petrels in different localities (x = major prey, o = minor prey, and * = incidental prey species).LocationDietCRUSTACEANCOELENTERATEECHINODERMCEPHALOPODFISHEuphausiidAmphipodCopepodDecapodLarvaeBarnacle"Fish"EngraulisMyctophidSebastesAmmodytesCarrion, fish offalFish eggsBlack-footed albatross(Diomedea nigripes)No. Pacific (Palmer 1962)xxxAleutian Islands (Cottam and Knappen 1939)oxoxxCalifornia (Miller 1936, 1940)ooxxxxLaysan albatross(D. immutabilis)No. Pacific (Palmer 1962; Bartsch 1922; Fisher 1904)xNorthern fulmar(Fulmarus glacialis)Pribilof Islands (Preble and McAtee 1923)oxAlaska (Gabrielson and Lincoln 1959)xxxOregon (Gabrielson and Jewett 1940)xNo. Atlantic (Hartley and Fisher 1936; Einarsson 1945; Fisher 1952)xxFlesh-footed shearwater(Puffinus carneipes)Australia (Oliver 1955; Serventy et al. 1971)xxxPink-footed shearwater(P. creatopus)California (Murphy 1936; Ainley, personal observation)xxE. Pacific (Cottam and Knappen 1939)xxBuller's shearwater(P. bulleri)SW Pacific (Falla 1934; Serventy et al. 1971)xxxPeru (Murphy 1936)xSooty shearwater(P. griseus)Aleutian Islands (Sanger, personal observation)xxxBritish Columbia (Martin 1942; Sealy 1973a)xxxOregon (Gabrielson and Jewett 1940)xCalifornia (Ainley, personal observation)xxPeru (Murphy 1936)xxxSW Pacific (Oliver 1955; Serventy et al. 1971)xxxShort-tailed shearwater(P. tenuirostris)Bristol Bay (Bartonek, personal communication)xAlaska (Cottam and Knappen 1939)xxxoNo. Pacific (Palmer 1962; Kuroda 1955)xxxAustralia (Serventy et al. 1971)xxxBass Strait (Sheard 1953)xMottled petrel(Pterodroma inexpectata)Pacific Ocean (Imber 1973)xE. No. Pacific (Kuroda 1955)xFork-tailed storm-petrel(Oceanodroma furcata)Pribilof Islands (Preble and McAtee 1923)xSE Alaska (Heath 1915)xBritish Columbia (Martin 1942)xCalifornia (Ainley, personal observation)xLeach's storm-petrel(O. leucorhoa)SE Alaska (Heath 1915)xCalifornia (PRBO, unpublished data)xxxxxSo. California (Palmer 1962)xxNo. Atlantic[31](Palmer 1962)xxxxx
Table 9.Diets of gulls in different localities (x = major prey, o = minor prey, and * = incidental prey species).LocationDietCRUSTACEANPOLYCHAETEMOLLUSCECHINODERMCOELENTERATEFISHCARRION-OFFALBIRDFISHEGGSEuphausiidBarnacleDecapodShellfishCephalopod"Fish"ClupeaEngraulisOsmerusPorichihysOtaphidiumMallotusBorrogadusMicrogadusGadusLycodesSebastesMyxocephalusGenyonemusEmbiotocidAmmodytesEggsChicksAdultsGlaucous gull(Larus hyperboreus)St. Lawrence Island (Fay and Cade 1959)xxxChukchi Sea (Swartz 1966)xxxxxxxPribilof Islands (Preble and McAtee 1923)xxxxxVancouver Island (Munro and Clemens 1931)xxGlaucous-winged gull(L. glaucescens)[32]Pribilof Islands (Preble and McAtee 1923)xxxxxxxAlaska (Bent 1921)xNo. Pacific (Sanger 1973)x**Mandarte Island (Ward 1973)xxxxxVancouver Island (Munro and Clemens 1931; Robertson, unpublished data)xxxWestern gull(L. occidentalis)[33]Farallon Islands (PRBO, unpublished data)xxo*x**xxoooxooxoooHerring gull(L. argentatus)No. Atlantic (Zelikman 1961)xE. No. America (Bent 1946; Ainley, personal observation)xxxxxx*oxVancouver Island (Munro and Clemens 1931)xxxMew gull(L. canus)Alaska (Bent 1921)xxxxVancouver Island (Munro and Clemens 1931)xxxHeermann's gull(L. heermanni)California (Bent 1921)xxxxBonaparte's gull(L. philadelphia)E. No. America (Bent 1921)xxxBlack-legged kittiwake(Rissa tridactyla)[34]Chukchi Sea (Swartz 1966)o*ooxooxPribilof Islands (Preble and McAtee 1923)oxoAlaska (Bent 1921)xoCook Inlet[35](Snarski, personal communication)oooxoxNo. Atlantic (Hartley and Fisher 1936; Zelikman 1961)xRed-legged kittiwake(R. breuirostris)Pribilof Islands (Preble and McAtee 1923)xxxSabine's gull(Xenia sabini)Pt. Barrow (Banner 1954)x
Table 10.Diets of terns in different localities (x = major prey species).LocationDietCRUSTACEANFISH"Crustacean"MallotusEuphausiidCottidAmphipodAmmodyteslarvaeArctic tern(Sterna paradisaea)Pribilof Islands (Preble and McAtee 1923)xxAlaska (Bent 1921)xxxNo. Atlantic (Hartley and Fisher 1936)xCommon tern(S. hirundo)E. No. America (Bent 1921)xx
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 1969b).
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).
Fig. 2. Schematic food web of the parakeet auklet in the eastern Bering Sea (based on Bédard 1969aand Dunbar 1946). Arrow sizes indicate relative importance of prey and Roman numerals refer to prey sizes (see text).
Fig. 2. Schematic food web of the parakeet auklet in the eastern Bering Sea (based on Bédard 1969aand Dunbar 1946). Arrow sizes indicate relative importance of prey and Roman numerals refer to prey sizes (see text).
Fig. 2. Schematic food web of the parakeet auklet in the eastern Bering Sea (based on Bédard 1969aand Dunbar 1946). Arrow sizes indicate relative importance of prey and Roman numerals refer to prey sizes (see text).
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.)SeabirdsHabitat, bird trophic levels (I-IV. Sc), and food categoriesOceanic and offshore neriticInshore neriticIIIIIIVScIIIIIIIVScCrustaceanPolychaeteCoelenterateFish/squideggs&larvaeFishCephalopodBirdsCarrion/offal/detritusPlantCrustacean,midwaterCrustacean,benthicCoelenterateEchinodermMolluscFish/squideggs&larvaeFish,midwaterFish,benthicCephalopodBirdsCarrion/offal/detritusGavia adamsii*oxG. arcticaoxPodiceps grisegenaooxDiomedea nigripesxoooxxxFulmarus glacialisxoxoxxxPuffinus griseusxxxooP. tenuirostrisxoxooOceanodroma furcataxooxxxxPhalacrocorax auritusoxoP. pelagicusxxP. urilexxBranta berniclaxPhilacte canagicaxClangula hyemalisoxooHistrionicus histrionicusoxoPolysticta stellerioxooSamateria mollissimaxoxS. spectabilisoooxS. fischerixxMelanitta deglandixoM. nigraooxHaliaeetus leucocephalusxxxFalco peregrinusxPhalaropus fulicariusxxoxxLobipes lobatusxxoxxStercorariusspp.oxx?xxxxLarus hyperboreusooooooooooxxxL. glaucescensooooooooooxxxL. argentatusooooooooooxoxL. canusxoooxxRissa tridactylaxxxoXema sabinixxooSterna paradisaeaxxooUria aalgexoxxooxoU. lomviaxoxxoxoxLunda cirrhata?xxFratercula corniculata*xxCepphus columbaoxoSynthliboramphus antiquusxxoBrachyramphus brevirostrisxoCyclorrhynchus psittaculusxo**Aethia cristatellaxxA. pusillaxo