On 26 November 2004, the MIT Athos 1 incident resulted in the release of an estimated 265,000 gallons of crude oil into the Delaware River System during a very dynamic period of bird migration in the region. The unique nature of the spill area, large numbers of birds, and complicating migratory activity required a novel approach. This effort, based on a large and high-quality field data set, represents one of the most complex risk-based damage assessments performed for birds injured during an oil spill to date. The approach estimates injury, both direct and indirect, while accounting for changing populations and oiling rates across time and in different areas for multiple guilds. During and after the spill, field teams conducted extensive aerial and ground surveys. Data from ground and aerial surveys were used in a rigorous risk-based assessment to estimate the extent of bird and wildlife losses resulting from the MIT Athos 1 incident. The total number of birds present in the area was estimated from detectability-adjusted aerial survey data for nine species guilds in three time periods. The number of birds in different oiling categories for each of these same guilds and time periods was estimated from ground survey data. This oiling information was then used to estimate the number of birds that were oiled and died in the field, or that survived with sublethal impacts. These estimates, combined with data from the wildlife rescue and recovery effort, were used to determine the total number of birds impacted (i.e. direct injury). Production foregone due to the loss of future generations (i.e. indirect injury), was included in the estimation of total injury as the discounted loss of production from dead individuals, and individuals that were oiled and survived, but then failed to reproduce. Demographic and reproductive statistics for model species from each guild were used to estimate this loss with age-structured population models.