While wind power is a promising source of renewable energy, there have been persistent questions about the safety of migrating birds in the presence of wind farms. In this paper we develop a framework that allows us to consider the costs and benefits of a very simple strategy: curtailing (turning off) the turbines during high-risk periods for endangered species. We develop a model that allows us to find the lowest financial cost strategy (where cost is represented in dollars) for the curtailing operation, given a specific goal for bird mortality reduction. We apply the model to a specific case study: the proposed Cape Wind project and the vulnerability of the common loon (Gavia immer), during one month of the migratory season. We calculate probability distributions over energy produced, price, and revenue to the wind farm, as well as over the numbers of loon mortality, and perform an uncertainty analysis. As an example, we find that with the goal of reducing 10% of the expected bird deaths during the month of March, the cost per bird averages $170, using the most cost effective curtailment strategy.