Poling of lead zirconate titanate pyroelectric thin films has been studied. Poling temperature and electrical field were optimized to achieve high figures of merit. We have found a direct correlation between the onset of degradation current and the final pyroelectric coefficient showing that thermal activation for defect motion is imperative for poling. We have proposed that defects and defect dipole complexes play a major role to obtain stable and metastable domain configurations after dc poling at high temperature and field cycling, respectively.