EXXON VALDEZ Oil Spill Restoration Project 93033-1 Final Report. Restoration Monitoring of Harlequin Ducks ('Histrionicus histrionicus') in Prince William Sound and Afognak Island, Alaska

摘要

The authors monitored densities of molting harlequin ducks and broods in the oil spill area of western Prince William Sound (WPWS) and in the non-oiled eastern area (EPWS) during July and August 1993. The shoreline density indices of molting harlequin ducks in WPWS was consistently lower than those in EPWS, at 1.29/km in 1991, 0.92/km in 1992, and 1.34/km in 1993. Density indices in EPWS were relatively stable, averaging 2.04/km, but were 1.6, 2.0 and 1.6 times greater than in WPWS during 1991-1993. These data indicate that the densities of molting harlequin ducks were greater in the unoiled portions of PWS, suggesting differential use because of oil effects or regional ecological differences. Differences in survey timing and coverage among years contributed an unknown margin of error in comparisons across years and regions. The shoreline density indices of broods in WPWS decreased 69% from 0.74/100 km in 1991 to 0.23/100 km in 1993. Densities of broods in EPWS averaged 2.02/100 km and were (respectively) 3.9, 7.1 and 7.8 times greater than in WPWS during 1991-1993, indicating that productivity declined in WPWS.