ABSTRACT Between the 1910s and the 1940s, American naturalists carried out a number of ornithological expeditions in Colombia. With the help of Colombian naturalists, thousands of skins were brought to natural history museums in the United States. By 1948 these birds had become an important treasure: American ornithologists declared Colombia the nation with the most bird species. This story sheds new light on the role science played in the expansion of U.S. political, economic, and cultural influence in Latin America in (...) the early twentieth century, as well as on the relation between nationalist movements in Latin America and the study of the natural world. Recognizing a complex but fruitful interaction between nationalist policies and imperial practices proves important for understanding the success of the naturalists' enterprise in Colombia. (shrink)