Recent tunneling spectroscopy experiments in semiconducting nanowires with proximity-induced superconductivity
have reported robust zero-bias conductance peaks. Such a feature can be compatible with the existence of
topological Majorana bound states (MBSs) and with a trivial Andreev bound state (ABS) near zero energy. Here,
we argue that additional information, that can distinguish between the two cases, can be extracted from Coulomb
blockade experiments of Majorana islands. The key is the ratio of peak heights of consecutive conductance peaks
gives information about the electron and hole components of the lowest-energy subgap state. In the MBS case,
this ratio goes to one-half for long wires, whereas for short wires with finite MBS overlap it oscillates a function
of Zeeman energy with the same period as the MBS energy splitting. We explain how the additional information
might help to distinguish a trivial ABS at zero energy from a true MBS and show case examples.