Post-Release Behavior of Surf Scoters (Melanitta perspicillata) Following an Oil Spill: An Experimental Approach to Evaluating Rehabilitation Success

Effectiveness of rehabilitatingwildlife following oil spills has been controversial. Impacts include mortality or changes in behavior affecting health or reproduction. Immediately following a bunker fuel oilspill on San Francisco Bay, California, USA, a unique experiment was conducted to examine the movement and foraging behavior of Surf Scoters(Melanitta perspicillata) that had been oiled, captured, cleaned, rehabilitated, and radio-marked. Unoiled Surf Scoterswere similarly cleaned, rehabilitated, and radio-marked while other unoiled Surf Scoterswere radio-marked as controls. Surf Scotersin the control group had larger home-ranges(46.29 ± 3.23 km2) than either the oiled/ rehabilitated(32.58 ± 5.48 km2) or rehabilitatedonly groups (31.06 ± 3.05 km2); the control group also was more likely to use unsheltered, shallow areas of the bay (66.9 ± 4.3% of locations) than either the oiled/ rehabilitated(50.3 ± 5.2%) or rehabilitatedonly groups (58.2 ± 6.5%). The oiled/ rehabilitatedgroup was closer to shore (986 ± 149 m) than rehabilitated(1,894 ± 295 m) or control groups (2,113 ± 227 m). Differences in habitat use, movement patterns, and home rangesizes indicated that Surf Scotersheld in captivity were more restricted in their movements; therefore, captivity and rehabilitationpractices may also influence success of the rehabilitation.