In the W7-AS stellarator, intense magnetic mode activity, observed in low confinement, NBI heated plasmas, was previously discussed in terms of marginal global Alfven eigenmodes that are destabilized by beam-wave resonances of the fast circulating beam ions. In the present work a kinetic interpretation is provided in which the resonance takes place between the trajectories of fast ions and the phase velocity of the wave, and forms an island in the toroidal surfaces formed by the trajectories of fast ions. The W7-AS stellarator has an extremely low shear, which makes it feasible to distinguish between waves that resonate with fast ion trajectories (and form 'trajectory islands') and waves that resonate with the magnetic field lines (and form magnetic islands)