The Tigre river basin in the Amazonian lowlands of northern Perú harbors a hyperdiverse avifauna that remains under-surveyed and poorly known. We conducted the first comprehensive ornithological inventory of the basin. Observational fieldwork at 42 sites spread across the Peruvian portion of the basin resulted in a bird list of 584 species, reflecting several noteworthy patterns in the avian biogeography of northern Perú. These patterns include the distribution of several species that specialize on nutrient-poor habitats, such as weathered clay terraces and peatlands. Peatland forests are especially poorly studied in Perú and represent a novel habitat association for these species. We also report on the presence of a suite of species with primarily montane distributions that occur in low density across the Amazonian lowlands and in the study area. Current conservation challenges in the Tigre basin include deforestation and pollution associated with hydrocarbons extraction and infrastructure projects.