Out in the wild, far from any artificial light, the difference between a full moon and a new moon (when the moon appears invisible to us) can be the difference between being able to walk outside without a flashlight and not being able to see the hand in front of your face. Over seven months, she discovered that when a full moon was visible in the sky, males started singing about 10 minutes earlier on average than when there was a new moon, York and colleagues reported in Biology Letters in 2014. The extra light, rather than some other aspect of the lunar phase, kick-starts the singing, the team concluded, because on days when the full moon is already below the horizon at dawn, sparrow weavers start crooning on their normal schedule.