In bird and mammal biology, altricial species are those whose newly hatched or born young are relatively immobile, have closed eyes, lack hair or down, and must be cared for by the adults. Altricial young are born helpless and require care for a comparatively long time. Contrast to precocial.

There are eight recognized rankings of development precocity as discussed in Precocial and Altricial Young  (http://www.stanfordalumni.org/birdsite/text/essays/Precocial_and_Altricial.html).