Precociality and altriciality

A diagram of altricial and precocial bird species

Precocial (/prɪˈkəʊʃəl/) species in birds and mammals are those in which the young are relatively mature and mobile from the moment of birth or hatching. They are normally nidifugous, meaning that they leave the nest shortly after birth or hatching. Altricial species are those in which the young are underdeveloped at the time of birth, maturing with the aid of their parents. These categories form a continuum, without distinct gaps between them.

A young chick stands up. Chickens are precocial birds and can stand shortly after hatching.

In fish, this often refers to the presence or absence of a stomach: precocial larvae have one at the onset of first feeding whereas altricial fish do not. Depending on the species, the larvae may develop a functional stomach during metamorphosis (gastric) or remain stomachless (agastric).

Altricial young birds

California quail chick (Callipepla californica), a precocial chick