Oil spills affect aquatic birds on individual, population, and ecosystem levels. Communities have responded to environmental accidents and have cared for oiled birds for as long as the damaging effects of oil exposure have been realized. Not until the Exxon Valdez disaster occurred, however, was there the political climate necessary to facilitate and fund organized oiled wildlife responses in the United States. Federal and California law now supports the infrastructure necessary to respond rapidly and efficiently to oil spills affecting wildlife. This improved infrastructure has resulted in access to appropriately designed and equipped facilities. trained staff and volunteers, and research improving medical management and bird survival.

The Unocal-Metrolink oil spill of 21 February 1995 resulted in approximately 7800 barrels of San Joaquin crude oil being deposited into the San Gabriel River in Huntington Beach, CA, USA. In order to determine long-term pathological effects of oil exposure and rehabilitation, hematological and serum biochemical parameters for both rehabilitated (RHB) American coots (Fulica americana) and reference (REF) coots were examined every 3-4 weeks (56, 81, 108 and 140 days post oil exposure) after birds were cleaned, rehabilitated and soft-released. Most significant differences in monthly comparisons between RHB and REF birds occurred 56 days following oil exposure. Total white blood cell (WBC) count, albumin:globulin (A:G) ratio and calcium concentration were higher in RHB birds compared to REF birds 56 days post oil exposure. In addition, mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase and creatine kinase activities, and creatinine, total protein (TP) and globulin concentrations were lower in RHB birds. Blood results from 56 days post oil exposure for RHB coots which subsequently died were compared to blood results from days 108 and 140 for REF coots which survived. Oiled and rehabilitated birds which died had significantly higher WBCs, packed cell volume, TP and globulin concentrations, and lower A:G ratio, MCH, MCHC, glucose and sodium concentrations compared to REF birds which survived. Blood result differences detected at 3-4-week intervals between RHB and REF survivors, and differences detected between RHB coots which died and REF coots which survived, suggested that RHB coots developed an inflammatory response (infectious or non-septic) and, concurrently, may have experienced decreased immune responsiveness. Additionally, RHB coots experienced either an iron (Fe) utilization or Fe metabolism problem. These pathophysiological mechanisms were consistent with increased hemosiderin (stored Fe) present in the liver, spleen and kidney of necropsied RHB birds, and may have contributed to RHB coot mortality. When blood parameter differences were examined for their impact on survival time, it was determined that RHB coots had shorter survival times if they had very high cholesterol (> or =449 mg/dl) or chloride (> or =110 MEQ/l) concentrations on day 56 post oil exposure. Interestingly, the lack of differences between RHB and REF coots from day 81 through day 140 suggested that, from a hematologic and clinical chemistry perspective, coots which were oiled, rehabilitated, released and survived at least 3.5 months could not be differentiated from wild (REF) coots. From these findings it appears that blood analysis, coupled with post-release survival data, may help discern reasons for increased mortality of oiled and rehabilitated birds, compared to non-oiled reference birds.

Oil spills occur on a worldwide basis from a variety of sources, including tanker ruptures, pipeline breaks, and oil well explosions. In addition to these large-scare events, a smaller number of birds are affected on a dairy basis from both petroleum and vegetable oil sources. The external effects of oil on wildlife include feather contamination resulting in ross of insulation, loss of buoyancy in water, and loss of flight ability as well as skin and ocular burns of varying severity. Internal effects result from inhalation and ingestion of toxic components that lead to pneumonia, gastrointestinal disturbances, hemolytic anemia, immune suppression, and organopathy. The rehabilitation of oiled wildlife involves field stabilization, correction of underlying physiological abnormalities before washing, proper washing and rinsing of arl contaminants, and assessment of set criteria before release. All wildlife care during an oil spill response is conducted in cooperation with state and federal trustee agencies and includes the collection of appropriate samples for legal documentation of affected individuals. Copyright (C) 1999 by W. B. Saunders Company.