This study investigated the effects of the Exxon Valdez oil spill on the use of oil-affected habitats by birds during 1989–1991. We measured densities of birds in bays that had been subjected to various levels of oiling from the spill during survey cruises that were conducted throughout the year in Prince William Sound (PWS) and during summer along the Kenai Peninsula. Overall, 23 of 42 (55%) species in PWS and 22 of 34 (65%) species on the Kenai showed no evidence of oiling impacts on their use of habitats. Most species that did show initial negative impacts had recovered by late summer 1991 when our study concluded, although 6 of the 19 species initially impacted in PWS and 6 of the 12 species initially impacted along the Kenai did not exhibit clear signs of recovery by this time. A Principal Components Analysis of species examined from PWS revealed extensive overlap in ecological attributes among species that were and were not negatively impacted in their use of oil-affected habitats. Species that did not show clear evidence of recovery tended to be intertidal feeders and residents of PWS, but other ecologically similar species evidenced either no initial impacts or rapid recovery. These similarities suggest that the prognosis is good for the species for which we were unable to document recovery in habitat use. Our findings, together with the rapid rates of recovery in habitat features reported in other studies, suggest that impacts of the Exxon Valdez oil spill on avian use of oil-affected habitats generally were not persistent.

In many materials, the dislocation structure after irradiation is observed to be heterogeneous, with regions of high dislocation density separated by ones of low dislocation density. Using a simple rate theory model with onedimensional diffusion of point defects (vacancies and interstitials), we show that spatial instabilities can arise for a general class of models for dislocation evolution. The numerical results obtained for density oscillations and their wave-lengths reproduce qualitatively both the magnitudes and trends with temperature of observed heterogeneous structures.

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