Retraction Note: The hidden fitness of the male zebra finch courtship song

The authors have retracted this article because, upon further analysis, one of the synthetic song pairs used in the female preference test (data in Fig. 3c,d) was shown to be reliable in its ranking of short versus long path length only 35% of the time and a second song pair was reliable only 75% of the time. Therefore, the authors have lost confidence in the ability to interpret these data. All authors agree to this retraction.