The nesting period for fledgling doves is just 11 to 12 days, according to East Valley Wildlife. If a baby doesn't leave after 12 days, its parents deny it food until it does so. There is a one-day gap between each baby's birth, so they leave in a staggered pattern.
The primary reason doves leave by the 12th day is that their body temperatures are regulated, and they no longer need warmth from parents. When doves aren't ready to fly by day 13, they often fall from the nest to the ground. They fly within a few days, though some fall victim to predators.