Definitions: precocial species, when hatched, have open eyes, are covered in down and leave the nest within two days of hatching.  There are three levels of precociality found in some North American species; altricial species have closed eyes, little or no down, must be fed by their parents, and are incapable of leaving the nest.  Bird behavior-P.R. Ehrlich et al.  Suggested readings: “The Birder’s Handbook published by Simon and Schuster; Peterson’s Field Guide Series J.M. Pasachoff “Stars and Planets” published by Houghton-Mifflin.