Bird fancier's lung (BFL) is a disease produced by exposure to avian proteins present in droppings, blooms, and serum of a variety of birds. Although serological test results are currently used to confirm clinical diagnosis of the disease, bird species specificity is poorly understood. This study aimed to contribute to a better understanding of the specificity of immunogenic proteins revealed from the droppings of three bird species. Sera from four patients with BFL and two controls without exposure were analyzed by Western blotting with antigens from droppings of two pigeon and budgerigar strains and two hen species. When the antigens from the droppings of the three bird species were compared, the profile of immunogenic proteins was different and there were similarities between strains of the same species. Only one 68-kD protein was common to pigeon and budgerigar droppings, while proteins of 200, 175, 140, 100, and 35 kD were detected as specific in one bird species. These results provide insight to further characterize these proteins, and to design new serological tests specific to different bird species. These tests may help to refine strategies of antigenic exclusion and also to allow a patient compensation in case of BFL of occupational origin.