[en] The Daya Bay Reactor Neutrino Experiment is designed to determine precisely the neutrino mixing angle θ₁₃ with a sensitivity better than 0.01 in the parameter sin²2θ₁₃ 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 are smaller than requirements.