A singularly perturbed system of differential equations can be reduced, in the singular limit, to a system in which the dynamics are given by the concatenation of two lower dimensional systems, called the fast and slow subsystems. Local and global bifurcations of the reduced system can imply similar bifurcations of the original system. Canards--solutions that remain close to unstable slow manifolds for a long time--play a key role in this analysis. I will present analyses and numerical studies of some of the bifurcations of periodic orbits of reduced systems. Examples will include the forced van der Pol system and models of coupled neurons.