Female harlequin duck winter survival 11 to 14 years after the Exxon Valdez oil spill

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In the mid- to late 1990s, nearly a decade after the 1989 Exxon Valdez oil spill, female harlequin ducks (Histrionicus histrionicus) suffered reduced winter survival in oiled areas of Prince William Sound, Alaska, relative to unoiled areas. The authors conducted follow-up studies from winters 2000–2001 to 2002–2003 to determine whether differential survival persisted and to evaluate whether individual-level indices of oil exposure were related to survival. Using radiotelemetry, they tracked 138 female harlequin ducks from November through March over three winters. Variation in survival was analyzed in relation to season, area oiling history, age class, body mass, and an index to exposure to residual oil based on cytochrome P4501A (CYP1A) induction. The authors determined that survival was most strongly related to season and age class, with evidence of higher survival in late winter and after hatch year (AHY) categories, respectively. Cumulative winter survival was estimated for AHY females to be 0.837 (±0.064) and 0.834 (±0.065) on unoiled and oiled areas, respectively; and hatch-year female cumulative winter survival was estimated at 0.766 (±0.138) on unoiled areas and 0.758 (±0.152) on oiled areas. Despite persistence of oil in some intertidal areas and evidence of contaminant ingestion by harlequin ducks during and beyond this study, neither area nor CYP1A were strongly related to variation in survival, suggesting that direct effects of the oil spill on harlequin duck demography had largely abated by the winters 2000–2001 to 2002–2003. These findings offer an unprecedented description of the timeline of effects of exposure to spilled oil and contribute to a body of literature that describe demographic effects of the Exxon Valdez oil spill that persisted over a much longer time than previously assumed. An appreciation for the timescale of chronic effects of oil spills, as well as potential for demographic effects related to much lower concentrations of oil than during the immediate period of acute effects following a spill, will provide wildlife managers with a basis for risk assessment and plans for mitigation when confronted with large spills or chronic pollution.

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ELECTRONIC FILE - Zoology

SWAP (2/19/2016) citation:
Esler D, Iverson SA. 2010. Female harlequin duck winter survival 11 to 14 years after the Exxon Valdez oil spill. . [accessed 2015 Jun 1]; Journal of Wildlife Management. 74(3):471–478. http://onlinelibrary.wiley.com/doi/10.2193/2008-552/abstract.