We examined the effects of the Exxon Valdez oil spill on mid-summer habitat occupancy by marine-oriented birds during 1989–2001 in Prince William Sound, Alaska, by extending our earlier 1989–1991 data set and analyzing the entire data set as a time-series. Intertidal habitats in the spill-affected area have been recovering, as indicated by significant temporal increases in the proportional coverage of rockweed (Fucus) and mussels (Mytilus) in oiled bays. Of the 25 bird species we examined, 12 (48%) exhibited no evidence of impacts, 10 (40%) exhibited negative impacts that subsequently disappeared, and 3 (12%) exhibited positive relationships with oiling that subsequently disappeared. No species provided clear evidence of delayed impacts, and all of the impacted species exhibited recovery by 2001. In comparison with our 1989–1991 study, we detected a slightly greater proportion of initial spill impacts in this study and were able to document recovery in habitat occupancy of several species that had not recovered by 1991. The present study, however, incorporates 1984 baseline data and a longer time-period for examination of impacts and recovery. Differences between our conclusions and those of other researchers on the effects of the Exxon Valdez oil spill on habitat use by birds may reflect differences in study design, criteria used to assess impacts and recovery, and definitions of “recovery.” These differences illustrate the difficulties of evaluating the consequences of environmental accidents, even large ones.

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