Marra's research in avian conservation science has three broad themes, including the ecology of migratory birds, urban ecosystem ecology and disease ecology. Marra's primary interests lie in understanding the factors that control population persistence and dynamics, so his research examines the roles of climate, habitat, food and pathogens, as well as other direct sources of mortality on the individual condition of both individual migratory and resident birds and their populations.
Marra's research is both fundamental and applied, and emphasizes incorporating events throughout the annual cycle to understand how more complex interactions across seasons drive the ecology and evolution of life-history strategies. To that end, Marra is ambitiously pursuing technological solutions to track animals, from dragonflies to bats, throughout their lifetimes.
Marra has founded several large research and communication initiatives, including Neighborhood Nestwatch, The Migratory Connectivity Project and the Animal Mortality and Monitoring Program. Communicating his science and his excitement for the conservation of wildlife to as wide an audience as possible, including the general public, is a high priority of his overall program.