  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 give 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, while 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.
