A method for monitoring the operation of a wind energy plant having at least one blade angle adjustable rotor blade. Rotor blade vibrations are registered during operation by at least one measuring device, and at least one current natural frequency is established from the registered vibrations. At least one environmental parameter and/or at least one operational parameter, which influence the natural frequency of the rotor blade, is or are additionally registered. At least one natural frequency expected value dependent on the additionally registered parameter(s) and at least one confidence interval are calculated for the at least one established current natural frequency of the rotor blade, and whether the established current natural frequency lies within, or outside of, the confidence interval around the natural frequency expected value is monitored. Also disclosed is an operational control apparatus of a wind energy plant and a corresponding wind energy plant.
