Estimates of seabird mortalities from an oil spill are imprecise; they may differ by thousands of birds. It is believed that only a small fraction of the birds killed in a spill wash up on the shore. Some authors have even speculated that the death rate at sea could range from 6 to 25 times the number washed ashore (Tanis and Mörzer-Bruyns 1968).
In contrast to terrestrial birds and semiaquatic species (e.g., ducks; geese; coots, Fulica spp.; or gulls, Larus spp.), totally seaborne species have a restricted reproductive potential. Many, such as the alcids, do not breed until they are 3 or more years old, and lay only one egg per year. Only one in five survives to go to sea.
Until about 5 years ago we knew little about seabirds. They are not game species (they taste fishy) and thus do not constitute an important economic resource. They have never been the subject of intensive waterfowl management or research by either State or Federal governments.
During the last 5 years a small group of people here and in England have been studying marine birds—their distribution, population status, physiology, diseases, and husbandry in captivity. Four organizations have primarily been involved: The American Petroleum Institute (API); the Wildlife Rehabilitation Center at Upton, Massachusetts; England's Advisory Committee on Oil Pollution of the Sea; and the International Bird Rescue Research Center in Berkeley, California. They have encountered many common biological and people problems, some of which I discuss here.
Biological Problems
The recuperation record for oiled seabirds in the past has admittedly been dismal. A few birds have been returned to nature, but only after a long and costly period of care. In the process, semidomestication often takes place. The percentage of cleaned birds that actually survive after release is even smaller. One should not infer from this small percentage that rehabilitated birds cannot readjust to life in the wild. Several successful reintroductions have been documented. U.S. Fish and Wildlife Service bands were returned from two western grebes that were cleaned and released after the 1971 San Francisco spill. One bird was picked up a year later near Treasure Island, California, and the second after almost 2 years, in the State of Washington (Fletcher 1973).
Survival rates have zoomed with recent strides in cleaning technology and husbandry. The International Bird Rescue Research Center reported a survival rate of 41%, based on hundreds of birds and about 20 different species over a 2-year period (Smith 1975). In South Africa, where powdered clay was used as a cleaning agent on jackass penguins, nearly 50% survived, although exact percentages have not been published (Edwards 1963; Holmes 1973). Rapid retrieval, the relatively small groups of birds treated, and expert cleaning and husbandry techniques are largely responsible for high success ratios. Rehabilitation success is measured not only in terms of percent survival but also in terms of median length of captivity and average cost per bird.
Rescued oiled birds arrive at cleaning centers under a wide range of physical conditions. Before capture they may have spent hours or days in water, during which their energy has been continuously drained. The oil destroys the bird's protective insulation, and metabolic rate must be increased to sustain body temperature. Constant preening also takes energy. Food demands increase, but feeding attempts, especially for diving birds, are thwarted by oil-fouled plumage. A bird may arrive at the cleaning center under stress, chilled, exhausted, dehydrated, starved, and ill from ingested oil. Cold weather accentuates these conditions. Often such birds are jammed together with other species, hauled long distances, and immediately put through a series of cleaning processes that would leave even a healthy bird weak and in a state of shock. One marvels at the stamina of the survivors.
In most past spills, every bird found was routinely cleaned regardless of its condition. Instead of attempting to reclaim all birds, a selective judgment should be made. If a bird's physical condition makes its chances of survival nearly impossible, it should be humanely killed (except for rare or endangered species). This would enable workers to devote more time and care to birds having a reasonable chance at survival.
Fletcher (1973) stated that many variables affect bird survival: weather conditions, the type and amount of oil in and on the bird, the species, the distance of the spill from the shore, the time lag from initial fouling until initial treatment, the degree of stress a bird is subjected to, the husbandry techniques used, the time of release (the sooner released, the higher the apparent survival), the number of birds being cared for (the fewer birds being handled, the higher the survival rate), the quality of the facilities available, and the training and experience of the people handling the birds.