  The Daya Bay Reactor Neutrino Experiment is designed to determine precisely
the neutrino mixing angle $\theta_{13}$ with a sensitivity better than 0.01 in
the parameter sin$^22\theta_{13}$ at the 90% confidence level. To achieve this
goal, the collaboration will build eight functionally identical antineutrino
detectors. The first two detectors have been constructed, installed and
commissioned in Experimental Hall 1, with steady data-taking beginning
September 23, 2011. A comparison of the data collected over the subsequent
three months indicates that the detectors are functionally identical, and that
detector-related systematic uncertainties exceed requirements.
