EFFECTS OF THE EXXON-VALDEZ-OIL-SPILL ON BIRDS - COMPARISONS OF PRE-SPILL AND POST-SPILL SURVEYS IN PRINCE-WILLIAM-SOUND, ALASKA

We used data from pre- and post-spill surveys to assess the effects of the Exxon Valdez oil spill on the abundance and distribution of birds in Prince William Sound, Alaska. We conducted post-spill surveys duri ng mid-summer (1989-1991) in 10 bays that had been surveyed prior to t he spill (1984-1985) and that had experienced different levels of init ial oiling from the spill (unoiled to heavily oiled). We evaluated whe ther there were changes in overall abundance across all bays between t he pre-spill and post-spill sampling periods, and changes in abundance in unoiled/lightly oiled bays versus moderately/heavily oiled bays th at would suggest oiling impacts. Of 12 taxa examined for changes in ov erall abundance, 7 showed no significant change, 2 (Bald Eagle and Gla ucous-winged Gull) increased in abundance, and 3 (Red-necked Grebe, Pe lagic Cormorant, and Pigeon Guillemot) decreased in abundance during a ll three post-spill years. Of the 11 taxa examined for differences in use of oiled versus unoiled habitats, 7 showed no significant response , 1 (Black-legged Kittiwake) exhibited a positive response to oiling, and 3 (Pelagic Cormorant, Black Oystercatcher, and Pigeon Guillemot) e xhibited negative responses to initial oiling. We conclude that the im pacts of this oil spill on abundance and distribution of birds were mo st evident in 1989, the year of the spill, and were most pronounced fo r Pigeon Guillemots. By 1991, signs of recovery were evident for all t axa that showed initial oiling impacts.