Restoration of common loons following the North Cape Oil Spill, Rhode Island, USA
Oil spills are a widespread problem in the marine environment and can have extensive acute and chronic adverse impacts to resident and migratory biota. On 19 January 1996, the North Cape oil tanker caught fire and grounded on the coast of Rhode Island resulting in the spill of 828,000 gal (3134 metric tonnes) of home heating oil. It resulted in the estimated death of nearly 2300 birds, including a projected 402 common loons (Gavia immer) and 12 red-throated loons (Gavia stellata). Based on existing demographic data, a resource equivalency analysis (REA) calculated that the total loss, as measured through dead adults and their foregone young over their expected lifetimes, was 2920 discounted loon-years. To generate compensatory loon years, it was initially estimated that 25 common loon nests would need protection from development for 100 years. Following a $3 million settlement with the parties responsible for the spill, we conducted surveys to identify the highest quality breeding loon habitat for protection. Monitoring efforts included 184 loon territories from 2000 to 2009, representing 866 loon territory-years on 70 lakes in four regions of Maine. To evaluate restoration effectiveness, an updated REA was conducted using productivity data collected from these surveys. Results from the updated REA indicated that were these site-specific data available when the REA was originally generated, 70 nests would have been required to offset the lost loon-years – this project permitted the protection of 119 nests. Future REAs should incorporate site specific productivity data whenever possible to most accurately scale restoration to injury. Ranking lake habitat quality further optimizes restoration effectiveness. Our results indicate breeding success was highest on 24–81 ha lakes and that emphasizing protection of lakes with loon territories in this size class is optimal. Our results demonstrate a need for site-specific restoration plans to achieve the greatest restoration benefits.