This interrupted case study introduces students to resource-based trade-offs and immune-based trade-offs, and the implications of these trade-offs on the spread of disease.  Students are first asked to interpret data on the energetically demanding portions of the annual cycle on black-capped chickadees (Poecile atricapillus) and how resource availability might differ during those periods. Students then apply what they have learned by analyzing data on the consequences of distributing energetic resources across multiple biological systems, like fat gain and the immune response. Finally, students are given data on parasite prevalence and intensity in the red grouse (Lagopus lagopus scoticus) / parasitic nematode (Trichostrongylus tenuis) system and are asked to make predictions about how populations might respond to a given resource limitation. This case study was designed for an upper-level undergraduate vertebrate animal physiology course, but could also be used in other courses including basic ecology, environmental physiology, disease ecology, animal behavior, and eco-immunology.