Why we put pepper in the bird feeder

Via Tangled Bank, Coturnix interprets research by Joshua Tewksbury and Gary Nabhan into the two-part evolutionary strategy of hot chili pepper plants: the fruits are brightly colored, soft, and sweet-smelling in order to attract birds, but unpleasantly spicy to repel mammals. The team fed peppers to birds (a species of thrasher, specifically), which passed the seeds in a viable state; but the seeds of peppers fed to packrats and cactus mice were usually partially digested.