Abstract

Due to potentially massive numbers of seabirds requiring care simultaneously during marine oil spill events, triage criteria are extremely important, both to maximize utilization of rehabilitation resources and to minimize the infliction of rehabilitation efforts on birds with poor prognosis. In 1953 the S.S. Jacob Luckenbach, a cargo vessel transporting post-war supplies to Korea, sank 17 miles off the Golden Gate Bridge in San Francisco CA, USA. In 2002, this ship was proven by chemical fingerprinting of oiled feather samples to be responsible for 'mystery spills' along the central California coast for more than a decade. This protracted spill provided the opportunity for collection of consistent data for several thousand live-stranded birds of more than 20 species. This study evaluated easily-measured standard data collected from birds stranding during 2001-2002, with the aim of identifying factors useful in providing guidance about which individuals to euthanize and which to treat during future spill events.

Medical records from 917 live-stranded, oiled common murres (Uria aalge) and 117 live-stranded, oiled Western Grebes (Aechmophorus occidentalis) were examined. Factors evaluated for predictive value included the following parameters: percent of body oiled, oil depth in plumage, body weight, mild, moderate or severe dehydration, normal vs prolonged capillary refill time, body temperature, body condition score, age category, packed cell volume (PCV), total plasma protein (TP), blood glucose (BG), presence of leg/skin lesions or development of later leg/skin lesions, respiratory problems (such as wheezes or crackles on auscultation) or development of later respiratory problems, pale mucous membranes, overt gastrointestinal bleeding, thermoregulatory problems, and regurgitation.

Factors for each species were evaluated individually and simultaneously, and were modeled using univariate and multivariate logistical regression. Factors found to be most predicative of survival to release included being more heavily oiled, having higher PCV, higher TP, higher body weight, and non-extreme body temperatures. Factors most predictive of death during rehabilitation included low PCV, low TP, low body weight, abnormally high or low BG, abnormally high or low body temperature, pale mucous membranes, pre-wash regurgitation and gastrointestinal bleeding. Factors found to have little or no value in predicting survival to release included oil depth, level of dehydration, capillary refill time, body condition score, or age category.

More heavily oiled common murres were found to have higher body weights (p<0.0005), higher PCV (p=0.006), and higher TP (p<0.0005) but body temperatures were not significantly different (p=0.49) from less oiled birds. Data was not available to ascertain whether higher body weight in more heavily oiled birds was due to the weight of the oil itself or the actual mass of the bird, but the significantly higher PCV and TP suggest that this difference is not mere artifact. We interpret this counterintuitive finding as more heavily oiled birds need to beach themselves sooner due to an immediate threat of drowning, whereas lightly oiled birds may postpone beaching until it is unavoidable due to exhaustion. All analyses were conducted utilizing SPSS v.16 (SPSS, Chicago IL, USA).

Acknowledgements

This study was supported by the Roy H. Hart Research Fellowship at University of California Davis School of Veterinary Medicine.