On the basis of this information it is possible to predict that alcids, which make up the bulk of the birds inhabiting the coastal areas during winter (Sanger 1972), would be very susceptible to oil spills from future tanker traffic in these waters. The potential exists, therefore, for a tremendous impact (from a single inopportune oil spill) upon these species and upon the entire ecosystem. Sea ducks too, because of their diving behavior, propensity for flocking, and flightless molt period, would be very vulnerable to oil spills. Wintering flocks of oldsquaws and several species of scoters along the coasts of Alaska, British Columbia, and Washington can be expected to dwindle as North Slope oil begins to be transported to Puget Sound ports.
It is recognized now that seabirds transfer and recycle nutrients and energy between trophic levels and between regions of an ocean (Sowl and Bartonek 1974). Although the significance of this role in the marine ecosystem can only be surmised at present, conservative estimates by Sanger (1972) indicated that birds consume from 0.6 to 1.2 million tons of food and return from 0.12 to 0.24 million tons of feces into the subarctic Pacific region annually. G. A. Sanger's (personal communication) revised estimates of these bird populations indicated that his 1972 estimates should be doubled. Regardless, it appears that the disastrous effects of such a spill would extend beyond the bird populations involved.
Indirect Effects of Oil Pollution and Petrochemical Developments
By no means would direct losses attributable to contamination by oil be the only threat to marine bird populations as a result of petrochemical expansions into these waters. Some water birds that become contaminated with nonlethal doses of petroleum during the breeding season are not likely to breed (J. M. Scott, comments by Pacific Seabird Group on U.S. Department of the Interior Draft Environmental Statement 74-90). Viability of embryos is greatly reduced when the eggshell becomes smeared with oil from the contaminated plumage of the female (Hartung 1965). Degradation of habitat, particularly to nesting areas and food supplies, will certainly occur, and its most pronounced effects will be felt in the Arctic. Gravel removal for construction of offshore drilling pads, causeways, and onshore production facilities would displace nesting birds and, combined with subsequent discharge of drill cuttings, perhaps have an adverse impact on bottom food organisms. Nesting habitat loss through destruction or the inability of birds to accept disturbance could be substantial, particularly along the Beaufort Sea coasts of Alaska and Canada, where offshore barrier islands and tundra-covered islands provide protection from mammalian predators for nesting by Pacific eiders, Sabine's gulls (Xemia sabini), Arctic terns (Sterna paradisaea), black guillemots (Cepphus grylle), and other species (Arctic Institute of North America 1974). Flaxman Island near the mouth of the Canning River is a tundra island supporting a nesting population of whistling swans (Olor columbianus), and the only nesting colony of the Alaska snow goose (Chen caerulescens) is on Howe Island in the Sagavanirktok River Delta (Arctic Institute of North America 1974).
Although there would probably be little actual nesting habitat loss for cliff-nesting species, human disturbance to colonies during the nesting period, particularly from helicopter and fixed-wing aircraft flybys, could have considerable impact (Sowl and Bartonek 1974). The "living waterfall" effect of thousands of seabirds pouring off a rookery is truly spectacular, but each such occurrence during incubation and brooding periods causes a rain of eggs or young to fall from the cliffs (Sowl and Bartonek 1974). Temporarily abandoned chicks and eggs are susceptible to predation by gulls or jaegers.
Even for species nesting on level ground, aircraft overflights close to breeding colonies may cause major losses to young and eggs. Sladen and LeResche (1970) reported that flights by an LH-34 helicopter (at 305 m altitude) over an Adelie penguin (Pygoscelis adeliae) colony caused some egg loss. Landing this aircraft 183 m from the colony caused 50 to 80% of the birds to flee territories, resulting in egg and chick loss. Disturbance caused by visitors walking through or near nesting areas of the South African gannet (Sula capensis) on Bird Island, Lamberts Bay, South Africa, caused desertion of nesting sites (Jarvis and Cram 1971). Studies of disturbance on breeding black brant, Pacific eiders, glaucous gulls (Larus hyperboreus), and arctic terns at Nunaluk Spit and Phillips Bay, Yukon, in July 1972 indicated that human presence was the most critical form of disturbance affecting incubating behavior of these species (LGL Limited 1972a). Disturbance by aircraft—especially helicopters—affected the normal incubating behavior of all species except Pacific eiders. Nesting success of black brant and arctic terns was reduced by this disturbance.
Disturbance can adversely affect molting birds. The process of molting places heavy energy demands on birds, and particularly on waterfowl whose molt results in a flightless period; few areas provide adequate protection from predators necessary during this period. Prime molting areas are scarce along the arctic coast, yet are vital to the welfare of thousands of sea ducks and seabirds. Studies conducted by LGL Limited (1972b) indicated that aircraft traffic over sea duck molting areas altered normal behavior, and therefore had a detrimental effect. Recommendations resulting from these studies were that air traffic be suspended over these areas during the molting season.
For some arctic-nesting waterfowl, premigration staging activity, during which fat reserves to sustain southward migration are stored, is a very important component of the annual cycle (Delacour 1964). Snow geese, breeding mainly in arctic Canada, concentrate in large numbers on staging grounds along the Beaufort Sea coast of eastern Alaska and the Yukon. Because gas compressor stations would be required along the proposed arctic gas pipeline route, experimental studies were conducted in September 1972 to determine the effect of disturbance from sounds generated by compressors (LGL Limited 1972c). These studies indicated that compressor noise was disruptive to staging geese.
Indirect effects on marine bird resources resulting from development activities may ultimately prove to be more detrimental than the aforementioned direct factors. It is conceivable that the impact of these industries, mainly on the benthic and demersal fauna of the coastal areas, could greatly lower the carrying capacity of this habitat for marine birds (Bartonek et al. 1974). Because of the simplified and short arctic food chains and the lack of alternative food sources in these areas, arctic ecosystems would be particularly vulnerable to this type of problem (Burns and Morrow 1973).