An evaluation of marine bird population trends following the Exxon valdez oil spill, Prince William Sound, Alaska

We examined post-spill trends (1989-1998) of marine bird populations in Pri nce William Sound (PWS) following the Exxon Valdez oil spill (EVOS) to eval uate recovery of injured taxa. Two criteria were employed. First, we examin ed population trends of injured tars only in the oiled area of PWS using re gression models, Second, we examined population trends of injured taxa in t he oiled area relative to the unoiled area using homogeneity of the slopes tests. We considered a population recovering if there was a positive trend using either criteria, we considered a population not recovering if there w as no trend using either criteria or a negative trend in the oiled area. A significant negative trend in the oiled area relative to the unoiled area w as considered a continuing and increasing effect. Most taxa for which injury was previously demonstrated were not recovering and some taxa showed evidence of increasing effects nine years after the oi l spill, Four taxa (loons Gavia spp, Harlequin Duck Histrionicus histrionic us, Bufflehead Bucephala spp, and North-western Crow Corvus caurinus) showe d weak to very weak evidence of recovery, None of these taxa showed positiv e trends in both winter and summer, Nine taxa (grebes Podiceps spp, cormora nts Phalacrocorax spp, Black Oystercatcher Haematopus bachmani, Mew Gull La rus canus, Glaucous-winged Gull Larus glaucescens, terns Sterna spp, murres Uvia spp, Pigeon Guillemot Cepplus columba, and murrelets Brachyramphus sp p) showed no evidence of recover) during summer or winter. Four taxa (scote rs Melanitta spp, mergansers Mergus spp, golden-eyes Bucephala spp, and Bla ck-legged Kittiwake Rissa tridactyla) showed evidence of continuing, increa sing effects. We showed evidence of slow recovery, lack of recovery, and di vergent population trends in many taxa which utilize shoreline and nearshor e habitats where oil is likely to persist. Potential lingering spill effect s and natural variability appeal to be acting in concert in delaying recove ry of many PWS bird populations, Published by Elsevier Science Ltd.