The confinement of energetic particles—including alpha particles, fast ions, and runaway electrons—is a critical issue in tokamak plasmas. Under strong magnetic field perturbations, the stochasticity of particle orbits can dramatically degrade confinement. This orbit stochasticity is commonly attributed to the overlapping of adjacent drift islands. While drift islands are often considered to resemble magnetic islands in form, the sideband resonance mechanism allows them to be influenced by magnetic perturbations of different mode numbers. A key question therefore arises regarding whether a drift island can exist in the absence of the corresponding rational magnetic surface. In this study, we demonstrate that a 1/1 drift island can indeed exist even when the minimum safety factor qmin>1, owing to the sideband resonance mechanism. An analytical model is developed to relate the kinetic safety factor qk in the core region to the magnetic safety factor q. The presence of rational values of qk determines whether the corresponding drift island can be excited. Calculations are performed separately for alpha particles and runaway electrons. For runaway electrons, the existence of a 1/1 drift island under a 2/1 magnetic perturbation is experimentally observed using synchrotron radiation imaging. Overall, these results clarify a key distinction between drift islands and magnetic islands, offering a reference for understanding energetic particle behavior in perturbed magnetic fields.