Some of the highest concentrations of microplastics, globally, have been reported in the Gulf of America, which is home to most plastic manufacturers in the United States. Microplastic ingestion not only poses a physical threat to humans and wildlife, but also an ecotoxicological threat from chemicals associated with plastic production and those readily adsorbed from the environment onto the plastic particles. A comprehensive understanding of the risk microplastic contamination poses to wildlife is critical to the development of scientifically sound mitigation and policy initiatives. However, very little knowledge exists regarding patterns of microplastic ingestion in Gulf of America birds or waterfowl in general, and specifically, no knowledge in Gulf of America waterfowl prior to this study. Here, we assess microplastic quantities and probability of ingestion for hunter-donated waterfowl from Texas and Louisiana. We collected carcasses of dabbling and diving ducks from hunters, dissected out the intestinal tracts, digested organics, filtered out microplastics, and counted them under a dissecting microscope. The probability of ingestion for wintering ducks from both states was approximately 60% with microplastic quantities ranging from zero to 80 microplastic pieces per individual. Microplastic fibers were overwhelmingly prevalent and 100% of ducks with detectable microplastic ingestion had ingested fibers.  Fragments, films, foams, foils, and nurdles were also all detectable at much lower percentages. The most prevalent microplastic colors were blue (~90% of ducks), and black, clear, and green (~85%, each), followed by red (~60%), white (~50%), and brown, yellow, and gray (<30%, each). Overall, our results suggest widespread ingestion of microplastics, and especially microplastic fibers, by wintering waterfowl in the northern Gulf of America. Future research is needed to understand the implications of this contamination for waterfowl health, productivity, and potential trophic transfer to humans.