Oil spills and Seabirds:

Assessing the Value of the Rehabilitation of Oiled Birds.

An essay for Ornithology 4620

by Neva Fudge (reproduced here by permission of the author)

Marine birds have been fouled with crude oil and other petroleum products for decades. It is estimated that 3.2 billion litres enter the oceans each year. 93.2% of this pollution is due to human carelessness associated with marine shipping operations, municipal and industrial runoff, etc. Oil pollution endangers many seabird populations. For example, the famous Exxon Valdez released over 36 400 tonnes of oil into the environment and killed an estimated 350 000-390 000 seabirds (Burger et al., 1993). However, birds are also effected by hundreds of smaller spills of petroleum and vegetable oils. The cumulative mortality of seabirds due to such chronic oiling can in some situations, exceed the more publicized deaths which follow large catastrophic spills (Burger, 1993). Media coverage of large oil spills and their effects on coastal and marine wildlife and environments are often accompanied shortly thereafter, by images of volunteers cleaning, treating and ultimately releasing oiled seabirds that have been affected by the spill. However, recent studies suggest that, even after such cleaning and treating, mortality rates of oiled seabirds remain extremely high. The new evidence has created great controversy since bird rescue and release are costly. In the Exxon spill alone, $41 000 000 dollars were spent on the rescue of 800 seabirds. Despite the skepticism, rehabilitation programs continue, driven by the human impulse to attempt to alleviate the stress of oiled birds.

Until recently, it was believed that seabirds only suffered external affects from direct contact with oil spills. This was observed to change the property of the feathers, causing them to become matted. This lead to a reduction in the birds waterproofing, insulation, capacity for flight, buoyancy and ability to find food and water. Rehabilitation centers were set up with the help of many volunteers to save the surviving seabirds that were affected. The birds were first captured and their plumage was restored by removal of fouling agents along with the indications of regrowth of damaged and missing plumage. Health restoration was conducted through medical treatment, intensive care and abundant food to restore body weight and condition. Blood chemistry values in the ranges of normal individuals, normal behaviour and body mass comparable to healthy birds were required before release. This whole process lasted approximately two to three weeks (Anderson et al., 1996). In the past, this process seemed valid and rehabilitated birds left the center with normal body weights and behavior, leading to predictions of high survival and normal breeding. However, until recently, few follow up studies were conducted and the actual fate of the birds was uncertain.

New research involving the investigation of released birds survival, dispersal and reproduction, have indicated that current efforts to restore oiled seabirds are not as efficient as once thought.

One study that suggests this involved oiled Brown Pelicans in the Southern Bight (SCB). After being exposed to two oil spills in 1990 and 1991, the Pelicans were captured, rehabilitated and released. These spills affected 200 Pelicans in total. To monitor the survival and dispersal of these pelicans, 112 birds were colour and/or radio marked before release. Nineteen unoiled birds from the same Brown Pelican population in an unaffected area were also captured, marked and released for use as controls. It was documented for the following two years; oiled birds disappeared at a higher rate and experienced lower survival rates than controls. The oiled birds showed no breeding activity, or even association with breeding colonies, as compared to controls, which displayed normal breeding behavior. The affected Brown Pelicans also did not display post-breeding dispersal with the rest of the colony and controls, but instead remained at the SCB breeding grounds for 5-6 months (Anderson et al., 1996). The low survival rates and lack of breeding activity of the Brown Pelicans indicate that current rehabilitation procedures are not sufficient for treatment of oiled birds.

A similar study which investigated three species of oiled Common Murres, produced much the same results. A sample of 127 oiled birds were cleaned, ringed and released. For oiled, cleaned murres, post released life expectancy was only 9.6 days and long term recovery rates were 10-20% of those of non-oiled birds. Only 2 of 78 survived longer than a year and only 4 longer than 5 months (Sharpe, 1996). Werner et al. (1997) found similar results in a study of an even larger sample of 'rehabilitated' Common Murres. The results of these experiments indicate that the treatment of oiled birds is ineffective. Seabirds exposure to oil at sea evidently adversely affects them in ways not reversed by cleansing treatment.

It is possible that they may sustain numerous forms of physiological lesions after petroleum hydrocarbon ingestion, although they may not indicate, if any, outward signs of debilitation. Recent research has documented that sublethal exposure is known to increase susceptibility to disease, increase energy costs, perturb parental behavior and disturb hormone status (Eppley, 1992). Secondary effects of oil spills have the potential to reduce short or long term reproductive success, and may affect its longevity. Tertiary effects may also impact unexposed seabirds if their prey or predator populations are affected, or if parents are affected (Eppley et al., 1990).

New studies have suggested that immune suppression may present a significant barrier to the survival of rehabilitated birds. In the past, few studies have investigated the immune system since its many intercellular reactions are difficult to study and also, the effects of immune system injury are not evident until days or weeks later when mortality occurs (Briggs et al., 1997). This makes it difficult to relate cause to effect. According to new research however, high mortality rates and poor breeding success of released birds may be largely due to damage to the immune system (Briggs et al., 1997). This supports that the impact of spilled oil on seabird populations is greater and perhaps longer lasting than previously been appreciated.

Presently, direct data gathered at cleaning centers show a variety of lesions in birds liver and kidney tissues, gut mucosal damage, osmotic and electrolytic balances, haemolytic anaemia and depletion of subcutaneous and abdominal fat stores (Briggs et al., 1997). Consequences on the immune system include depression of leukocyte numbers and an adaptive shift in the bone marrow toward production of red blood cells to combat the effects of anaemia. This is evident in rehabilitation centers where bacterial and fungal infections are common among seabirds. Inflammation of the gastrointestinal tract following oil ingestion could lead to a variety of complications to the immune system. It reduces the absorption of nutrients, resulting in malnutrition. This causes the depletion of body fat, depression of T cell function and vitamin and mineral imbalances. Mineral imbalances such as zinc deficiency can take the form of immune depression spanning multiple generations (Beach et al., 1982). This trans-generational immune suppression could be disastrous to a population and might be important in cases like that of the Exxon Valdez spill in Alaska where impacted seabird population fail to completely recover (Warheit et al., 1996).

One in vivo study, which produced supporting evidence of immune suppression, involved Mallards, which were dosed with petroleum distillates and /or oil emulsifiers. The Mallards showed reduced ability to phagocytize and kill Pasteurella multocida, the agent of avian cholera (Rocke et al., 1984).

Obviously the effects of oil on the immune system are serious and cannot be cured through general treatment currently used in rehabilitation programs.

It has also been indicated that stress due to oil spills and rehabilitation also cause detrimental effects on seabird immune systems. Contamination with petrochemicals can cause the ocean environment to become very stressful to the seabirds. Loss of buoyancy and insulation, hampered feeding, multiple encounters with people and spill equipment, unfamiliar diet, unusual thermal and light conditions, crowding and handling are examples of stressors experienced by oiled birds.

It has been documented that the physiological stress experienced by seabirds exposed to petrochemicals causes increased concentrations or rapid metabolism of corticosteroids. Corticosteroids cause many immunosuppressive effects, such as destruction and redistribution of lymphocytes, blockage of lymphocyte activation (especially T cells), changes in response to food antigens, changes in metabolism of fat and protein (Briggs et al., 1997). These are yet more examples of serious effects caused by oil spills that cannot be restored through the use of current rehabilitation techniques. Instead, capture and handling enhance the stress on seabirds, increase their complications due to oil spills and further decrease their chances of survival.

Other indirect effects of oil pollution on seabird populations are not at all treatable by rehabilitation even if current methods were improved. This decreases the emphasis on rehabilitation and stresses the importance for prevention of oil spills or even developing methods of predicting their consequences.

These tertiary effects of oil spills are subtle and are often not documented, since it is difficult to prove the spill as the causative agent. These effects result from the manifestation of secondary effects. For example, impairment of parental behavior in caring for their chicks can produce profound effects on the reproduction of a seabird population.

The Bahia Paraiso oil spill in Antarctica had this effect on the South Polar Skuas in 1989. An estimated 1 000 000 litres of diesel fuel and jet fuel were spilled due to wreckage near the nesting areas of the seabird colony. Prior to the incident normal nesting behavior was observed. Approximately three weeks after the spill occurred, all South Polar Skua chicks had died, throughout the whole colony. Adults were observed foraging in oil slicks and becoming fouled, but there was no significant transfer to the chicks either through feeding or direct contact during brooding. Skuas defending their chicks were not visibly oiled and nestlings showed no symptoms of diesel poisoning, such as gastroenteritis. Also, growth rates were not lower than before the spill. Evidence showed that chick deaths were not due to starvation, toxicity, hypothermia, or abandonment. It was proposed that nesting skuas became fouled while foraging in oil slicks and went to freshwater ponds to bathe and remove light diesel coating from plumage. This cleansing, which usually occupied two hours of their daily routine, became extended to two days and delayed their return to the nest. This caused a short-term breakdown in pair coordination and nest attendance. Other skuas killed undefended chicks. Ultimately, all breeding pairs were affected and the entire population lost its young (Eppley et al., 1990). The cause of reproductive failure of the South Polar Skuas has been controversial due to the indirect influence of oil exposure. However, there is sufficient evidence to support that these effects were too prominent to be coincidentally due to, as some scientists may argue, natural variation.

The studies presented are part of a small but growing literature, which demonstrate the ineffectiveness of oiled bird rehabilitation. It seems that all recent research indicate that the rescue of seabirds is not a sufficient method of dealing with the problem of oil pollution. However, there are a few studies that show otherwise. In one study that monitored oiled Mute Swans that were rehabilitated in captivity without cleaning or extensive handling, then liberated them 30-101 days later. They found increased mortality in the five month period after release along with general failure to breed the season following oiling. Both effects were then followed by a return to normal by about the second breeding season (Collins et al., 1994). Therefore by decreasing the amount of handling and stress on the birds, the effectiveness of the rehabilitation was increased.

Other measures can be used to increase the value of cleaning facilities. First there should be an improvement of clinical evaluation of immune competency. Birds should not be released from cleaning centers until appropriate measures of immune function have returned to norms characteristic of birds in the wild. This can be achieved by serial measurement of circulating immune cell populations, routine monitoring of blood chemistry and corticosteroid levels (Briggs et al., 1997). Other studies have demonstrated that acute phase proteins can be used as measures of ongoing immunosuppression and inflammation (Fowler et al., 1995).

Direct measures of immunocompetency should be used, for example cutaneous hypersensitvity reactions. Small amounts of mitogenic compound are injected into an easily accessible spot and the degree of inflammation is assessed hours or days later. This is a powerful in vivo test of integrated immune responses.

The use of immunomodulators can also boost performance of immune cells. One study stated that HMB, a metabolite of dietary leucine has been shown to improve survival and growth in a variety of domestic birds and mammals under stress of production husbandry.

The evidence points to the conclusion that cleaned birds are unfit, in the survival sense, at release. Despite the stacking evidence, society is compelled, either by its compassion for the helpless birds, or the guilt that their suffering is due to the carelessness of their own race, to continue to rehabilitate oiled birds. Obviously, current methods are inefficient, and improvements must be made if we are to make effective use of our time and money. There is some hope, since studies show that even small improvements make a large difference in the survival of released birds. However, not all effects can be cured through treatment, such as in the case of the South Polar Skuas. It has been suggested that new methods of predicting the environmental consequence of spills should be developed. However, in my opinion, research should not concentrate on how to deal with the consequences after they occur but should emphasize ways in which we can stop them from occurring. As they say, prevention is the best medicine.

References

Anderson, D., Gress, F. & Fry, D. M. (1996). Survival and Dispersal of Oiled Brown Pelicans After Rehabilitation and Release. Marine Pollution Bulletin, 32: 711-718

Beach, R.S., Gershwin, M. E., and Hurley, L. S. (1982). Gestational Zinc Deprivation in Mice: Persistence of Immuno-deficiency for Three Generations. Science, 218: 469-471.

Briggs, K. T., Gershwin, M. E., and Anderson, D. W.(1997). Consequences of Petrochemical Ingestion and Stress on the Immune System of Seabirds. ICES Journal of Marine Science, 54: 718-725.

Burger, A. E. (1993). Estimating the Mortality of Seabirds Following Oil Spills: Effects Of Spill Volume. Marine Pollution Bulletin, 26: 140-143.

Collins, R., Brazier, H. and Whelan, J. (1994). Rehabilitating a Herd of Oiled Mute Swans Cygnus olor. Proc. Royal Irish Academy, 94: 83-89.

Eppley, Z. A. (1992). Assessing the Indirect Affects of Oil in the Presence of Natural Variation. Marine Pollution Bulletin, 25: 307-312.

Eppley, Z. A. and Rubega, M. A. (1996). Indirect Effects of an Oil Spill: Reproductive Failure in a Population of South Polar Skuas Following the Bahia Pariaso, Oil Spill in Antarctica. Marine Ecological Progress Series, 67:1-6.

Sharpe, B. E. (1996). Post Release Survival of Oiled, Cleaned Seabirds in North America. Ibis, 138:222-228.

Rocke, T. E., Yuill, T. M. and Hindril, R. D. (1984). Oil and Related Toxicant Effects on Mallard Immune Defences. Envir. Res.,33:343-352.

Warheit, K. T., Harrison, C. S., and Divorsky, G. J. (1997). Exxon Valdez Oil Spill Restoration Workshop. Technical publication 1 of the Pacific Seabird Group (in Press).

Wernham, C., Peach, W. and S. Browne. 1997. Survival rates of oiled guillemots. BTO Research Report No. 186. (also summarized in Seabird Group Newsletter, 79, March 1998).

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