Young (usually birds) which hatch (or are born) at an early stage of development, and are helpless compared with precocial young. Altricial young depend greatly on their parents for food and protection, while precocial young are less dependent.
If we compare altricial and precocial young at the same stage of physical development, such as the point which the feathers first appear, we find that the precocial bird is still inside the egg, while the altricial bird has already hatched. By the time the precocial bird hatches, the altricial juvenile has had the opportunity to learn a great deal, while the precocial bird has not yet begun to learn. For example, the altricial white-crowned sparrow (Zonotrichia leucophrys) learns the song of its species while a nestling. In contrast, chickens (Gallus gallus domesticus) are precocial, passing early infancy while still in the egg, but they have the innate ability to produce normal vocalizations even though never previously exposed to them.
Subjects: Zoology and Animal Sciences.