We estimated the summer and winter abundance of marine birds in Prince William
Sound, Alaska, following the 1989 Exxon Valdez oil spill, examined changes in population size
between pre-spill and post-spill surveys, and compared pre- to post-oil spill population trends in
the oiled zone of the Sound relative to trends in the unoiled zone.
Ninety-nine species of birds were observed on surveys. Not all species were equally vulnerable to
the oil spill because of the seasonal and geographic distribution. Estimated populations of 15 to