Tidal marsh ecosystems are predicted to change significantly over the next century in the northern Gulf of Mexico. Sea level rise will inundate current habitat, erosion and accretion will build new marsh elsewhere, and saltwater intrusion will change vegetation communities and habitat structure over much of the region. For tidal marsh endemics like Clapper Rails (Rallus crepitans) these environmental changes create uncertainty in their future distribution and abundance. Complicating the issue further is our incomplete understanding of Clapper Rail life history in the northern Gulf of Mexico—in particular, our lack of data for adult and juvenile annual survival rates. To understand how changes to tidal marsh habitat influences endemic species, we conducted a study to collect the current best information on marsh bird abundance in the northern Gulf of Mexico and gather information on Clapper Rail survival to parameterize population models to predict future changes to these populations. In this study we were able to estimate population sizes for Clapper Rail and other marsh birds across the northern Gulf of Mexico to provide baseline patterns of abundance in the region. Using nanotag technology we estimated the annual survival of adult Clapper Rails and projected how tidal marsh habitat changes in the next 100 years influenced their population size and vital rates.