According to Parakeet Care, parakeet eggs take about 18 to 20 days before they start to hatch. When they do start to hatch, the hatchlings are completely helpless and rely on their mother for around-the-clock care.
When the chicks are about 10 days old they start to open their eyes. Parakeet Care states this is also the time that the chicks begin developing a feather down, and it's usually the best time to apply closed bands to the chicks' legs.
The chicks usually start to develop feathers at 3 weeks of age, at which point the coloring of each individual chick should be easily identifiable. This is also the stage at which the male parakeet begins to enter the nest or nest box to assist the mother in caring for and feeding the chicks. Some mothers may completely forbid the male from entering the nest or nest box, thus taking on sole responsibility of the chicks. If this occurs, and the resources are available, it may be best to transfer some of the chicks to another pair of parakeets. This pair must already be in breeding mode and therefore either be at the laying or incubating stages, or rearing their own hatchlings. The chicks should be able to survive on their own when they are 4 weeks old.