How long a baby bird takes to leave the nest depends on its species. Some, such as ducklings, leave the nest within 2 days. Eagles, on the other hand, take 2 to 3 months to mature enough to fly and remain near their home nests for several weeks afterward.
Ducklings are examples of precocial birds, which are birds that have open eyes and coats of feathers or down when hatched. These birds have the mobility to leave the nest soon after birth; in fact, one group of birds called megapodes is so well developed at hatching that hatchlings can fly almost immediately.
Eagles are examples of altricial birds, which are birds born in a less developed state that must be cared for by their parents. Songbirds, such as robins, are altricial but can mature enough to leave the nest in about 2 weeks.