Section 16 reporting and Incremental Performance Shares

Here are the facts:

Grant of performance stock award to a Section 16 reporting person.  The award of the target shares is reported on Form 4.

3 annual earning cycles, each with the opportunity to earn more shares than were granted if the performance metric exceeds 100% of target at the end of each cycle.

The grant cliff-vests one year after the end of the last earning cycle (target + incremental shares are 100% vested).

Is the earning of additional performance shares above the target granted shares at the end of each earning cycle, a reportable event for Section 16?

Or are the incremental shares reportable when they vest? (after all of the earnings cycles)