Table 2.Criteria and points used in calculating Oil Vulnerability Index.Point assignment135RangeBreedingLargeMediumSmallMigrationLongMediumShortWinterLargeMediumSmallMarine orientationCoastal zoneIntertidalOpen waterPopulationSizeLargeMediumSmallProductivityLargeMediumSmallHabitsRoostingShoreDriftWaterForagingWalkingFlyingSwimmingEscapeLeave areaFlyDiveFlockingSmallMediumLargeNesting densityLowMediumHighSpecializationLowMediumHighMortalityHunted by manLowMediumHighAnimal depredationsLowMediumHighNon-oil pollutionLowMediumHighHistory of oilingLowMediumHighExposureSpringLowMediumHighSummerLowMediumHighFallLowMediumHighWinterLowMediumHigh
With these points in mind it is immediately obvious that Southeast Alaska (Table 4), which has only 9 high-score birds, offers far less potential for bird problems than does the Aleutian area (Table 5), which has 24 high-score species. The planning agency could make some immediate decisions on site priorities and research funding based on such information.
We are convinced that the OVI principle expressed here will become a useful management tool with all sorts of possible applications. We recognize some difficulties with the present version, but believe it is timely to present the system so that a broader range of thought, improvements, and application can be applied to it.
Of prime importance is the system's simplicity. The use of four levels of value for each factor, instead of five or more, is an attempt to simplify. Ian McHarg (1969) has shown that extremely complex land-use values can be graphically compared and displayed by using three levels in a way that is useful to decision makers. The difficulty of using more levels of value was indicated by Sparrowe and Wight (1975) who used up to 10 levels, enormously complicating the problem of dealing with low-quality information, which is often all that is available. The use of scores of 0, 1, 3, 5 instead of 0, 1, 2, 3 for 20 factors enabled us to use the convenient 100 points instead of 60 points as the maximum potential total score for any species.
The 20 factors that were evaluated are admittedly arbitrary; with refinement and more detailed data they could be adjusted to show better separation between affected species. The decision to use 20 factors instead of more or less again relates to simplicity. This appears to be the minimum number that will assure species separation and that can be neatly displayed.
Table 3.Oil Vulnerability Index (OVI) for families of birds of the Northeast Pacific marine habitats, excluding rare and endangered species in the scoring.FamilyNumber of speciesTotal OVIOVI per speciesAverageRangeLoons—Gaviidae42195547-65Grebes—Podicipedidae31484944-56Albatrosses—Diomedeidae21025150-52Shearwaters—Procellaridae42085247-57Storm-petrels—Hydrobatidae21306563-67Cormorants—Phalacrocoracid42355952-63Herons—Ardeidae1292929Waterfowl—Anatidae331,7655332-78Eagles and Hawks—Accipitridae2773919-58Ospreys—Pandionidae1373737Falcons—Falconidae1414141Cranes—Gruidae1242424Rails and Coots—Rallidae1333333Oystercatchers—Haematopodidae1656565Plovers—Charadriidae72874126-57Sandpipers—Scolopacidae228573924-59Phalaropes—Phalaropodidae21206058-62Jaegers and Skuas—Stercorariidae31234139-43Gulls and Terns—Laridae167304632-66Auks—Alcidae151,1647870-88Kingfishers—Alcedinidae1282828Crows—Corvidae2683421-47Total and Mean1286,4905119-88
The system will be much more useful when it is expanded to the subspecific level. Many Holarctic species are represented in the Northeast Pacific by a single race that would have a much higher OVI than the species as a whole. For example, the OVI for the Peale's peregrine falcon(Falco peregrinus pealei)confined to marine habitats within the Pacific region would be high; and the endangered Aleutian Canada goose(Branta canadensis leucopareia)would score 100 points instead of the 34 we show for Canada geese(B. c.). If Tables 4 and 5 showed subspecies, the differences in value would be more marked.
Tables 4 and 5 are for broad geographical areas. A comparison between smaller areas would probably show more dramatic differences.
Because the dearth of easily available, applicable information poses a problem in evaluating the various factors, our scoring was conservative. Experts on the various avian families can doubtless refine the scoring. If this system proves useful, investigators will begin to acquire the information needed for more precise evaluations. Ultimate perfection may never be achieved; however, as with the field guides, the fact of minor professional disagreement should not destroy the system's utility.
We believe re-scoring of all birds on the basis of various projects should be avoided because a standard against which individual projects can be measured is needed. If everyone did their own scoring, there would be no standard, and projects evaluated by different investigators would not be comparable. If a species list for the project area and standard point scores are used, the level of involvement for many species and perhaps for most species will be properly identified. As with any system, there will be exceptions and the assessor will need to deal with these as appropriate. The result will still be to focus attention on those species and impacting factors where it is most needed.
Table 4.Oil Vulnerability Index for 109 species of birds of Southeast Alaska (Total Points—2,678).OVI 1-20OVI 21-40OVI 41-60OVI 61-80OVI 81-100Marsh hawk19Great blue heron29Common loon47Pelagic cormorant63Pigeon guillemot8252 species, rare or occasional (one point each)52Canada goose34Arctic loon58Oldsquaw66Marbled murrelet84White-fronted goose36Red-throated loon49White-winged scoter72Snow goose32Red-necked grebe44Surf scoter72Mallard36Horned grebe48Black oystercatcher65Pintail36Whistling swan50Northern phalarope62Green-winged teal34Trumpeter swan63Common murre70American wigeon36Greater scaup52Semipalmated plover28Lesser scaup52Killdeer26Common goldeneye48Common snipe29Barrow's goldeneye56Spotted sandpiper24Bufflehead52Greater yellowlegs30Harlequin duck60Lesser yellowlegs30Common merganser56Pectoral sandpiper32Red-breasted merganser56Least sandpiper34Bald eagle58Herring gull38Peregrine falcon41Bonaparte's gull40Black turnstone57Arctic tern32Rock sandpiper59Belted kingfisher28Dunlin41Common raven21Short-billed dowitcher41Western sandpiper47Glaucous-winged gull56Thayer's gull42Mew gull44Northwestern crow47Totals716651,324470166
Table 5.Oil Vulnerability Index for 123 species of birds of the Aleutian Islands(Total Points—2,689).OVI 1-20OVI 21-40OVI 41-60OVI 61-80OVI 81-10080 species, rare or occasional (one point each)80Canada goose34Fulmar57Fork-tailed storm-petrel67Pigeon guillemot82Least sandpiper34Slender-billed shearwater53Leach's storm-petrel63Whiskered auklet88Arctic tern32Greater scaup52Pelagic cormorant63Common raven21Common goldeneye48Red-faced cormorant63Bufflehead52Black Brant70Harlequin duck60Emperor goose70Bald eagle58Oldsquaw66Peregrine falcon41Steller's eider72Ruddy turnstone44Common eider68Rock sandpiper59King eider70Western sandpiper47White-winged scoter72Red phalarope58Common scoter72Parasitic jaeger43Black oystercatcher65Glaucous-winged gull56Red-legged kittiwake66Black-legged kittiwake49Common murre70Thick-billed murre70Ancient murrelet74Parakeet auklet80Crested auklet76Least auklet80Horned puffin72Tufted puffin72Totals801217771,541170
We have used our OVI system to show the vulnerability of birds to oil, but it seems likely that the vulnerability index could be applied on a much broader scale to help make decisions in other areas of human activity and resource development. The vulnerability index system could be applied to terrestrial as well as aquatic species by adding or subtracting impacting factors, as appropriate. Indexes relating the impact of man upon each North American species could have broad uses in the field of conservation. Population explosions, as well as declines, might be predictable. Human activity could be better adjusted to favor or depress wildlife populations, as appropriate.
We believe that this vulnerability index system has promise for aiding in the decision-making processes upon which future bird conservation will depend.
American Ornithologists' Union. 1957. Check-list of North American birds. 5th ed. Lord Baltimore Press, Baltimore, Maryland.Fay, F. H., and T. J. Cade. 1959. An ecological analysis of the avifauna of St. Lawrence Island, Alaska. Univ. Calif. Publ. Zool. 63(2):73-150.Gabrielson, J. N., and F. C. Lincoln. 1959. The birds of Alaska. The Stackpole Company, Harrisburg, Pa., and Wildlife Management Institute, Washington, D.C. 922 pp.Gibson, D. D. 1970. Check-list of the birds of Alaska. Univ. of Alaska, Fairbanks. 2 pp.Isleib, M. E., and B. Kessel. 1973. Birds of the North Gulf Coast-Prince William Sound region, Alaska. Univ. of Alaska Biol. Pap. 14. 149 pp.Kortright, F. H. 1942. The ducks, geese and swans of North America. Wildlife Management Institute, Washington, D.C.McHarg, I. L. 1969. Design with nature. Natural History Press, Garden City, N. Y. 197 pp.Murie, O. J. 1959. Fauna of the Aleutian Islands and Alaska Peninsula. U.S. Fish Wildl. Serv., N. Am. Fauna 61:1-364.Palmer, R. S. 1962. Handbook of North American birds. Vol. 1. Yale University Press, New Haven, Conn. 567 pp.Peterson, R. T., G. Montfort, and P. H. D. Hallom. 1967. A field guide to the birds of Britain and Europe. Houghton Mifflin Co., New York.Robbins, D. S., B. Bruun, and H. S. Zimm. 1966. Birds of North America, a guide to field identification. Golden Press, New York.Sanger, G. A. 1972. Preliminary standing stock and biomass estimates of seabirds in the subarctic Pacific region. Pages 589-611inA. Y. Takenouti et al., eds. Biological oceanography of the North Pacific Ocean. Idemitsy Shoten, Tokyo.Sparrowe, R. D., and H. M. Wight. 1975. Setting priorities for the endangered species program. Proc. N. Am. Wildl. Nat. Resourc. Conf. 40:142-156.Stout, G. D., P. Matthiessen, V. R. Clem, and R. S. Palmer. 1967. The shorebirds of North America. Viking Press, New York. 270 pp.U.S. Fish and Wildlife Service. 1974. Birds of the Aleutian Islands National Wildlife Refuge. Washington, D.C.U.S. Forest Service and Alaska Department of Fish and Game. 1970. Birds of Southeast Alaska, a check-list. The agencies, Juneau, Alaska. 12 pp.
American Ornithologists' Union. 1957. Check-list of North American birds. 5th ed. Lord Baltimore Press, Baltimore, Maryland.
Fay, F. H., and T. J. Cade. 1959. An ecological analysis of the avifauna of St. Lawrence Island, Alaska. Univ. Calif. Publ. Zool. 63(2):73-150.
Gabrielson, J. N., and F. C. Lincoln. 1959. The birds of Alaska. The Stackpole Company, Harrisburg, Pa., and Wildlife Management Institute, Washington, D.C. 922 pp.
Gibson, D. D. 1970. Check-list of the birds of Alaska. Univ. of Alaska, Fairbanks. 2 pp.
Isleib, M. E., and B. Kessel. 1973. Birds of the North Gulf Coast-Prince William Sound region, Alaska. Univ. of Alaska Biol. Pap. 14. 149 pp.
Kortright, F. H. 1942. The ducks, geese and swans of North America. Wildlife Management Institute, Washington, D.C.
McHarg, I. L. 1969. Design with nature. Natural History Press, Garden City, N. Y. 197 pp.
Murie, O. J. 1959. Fauna of the Aleutian Islands and Alaska Peninsula. U.S. Fish Wildl. Serv., N. Am. Fauna 61:1-364.
Palmer, R. S. 1962. Handbook of North American birds. Vol. 1. Yale University Press, New Haven, Conn. 567 pp.
Peterson, R. T., G. Montfort, and P. H. D. Hallom. 1967. A field guide to the birds of Britain and Europe. Houghton Mifflin Co., New York.
Robbins, D. S., B. Bruun, and H. S. Zimm. 1966. Birds of North America, a guide to field identification. Golden Press, New York.
Sanger, G. A. 1972. Preliminary standing stock and biomass estimates of seabirds in the subarctic Pacific region. Pages 589-611inA. Y. Takenouti et al., eds. Biological oceanography of the North Pacific Ocean. Idemitsy Shoten, Tokyo.
Sparrowe, R. D., and H. M. Wight. 1975. Setting priorities for the endangered species program. Proc. N. Am. Wildl. Nat. Resourc. Conf. 40:142-156.
Stout, G. D., P. Matthiessen, V. R. Clem, and R. S. Palmer. 1967. The shorebirds of North America. Viking Press, New York. 270 pp.
U.S. Fish and Wildlife Service. 1974. Birds of the Aleutian Islands National Wildlife Refuge. Washington, D.C.
U.S. Forest Service and Alaska Department of Fish and Game. 1970. Birds of Southeast Alaska, a check-list. The agencies, Juneau, Alaska. 12 pp.