(also altrices), a group of birds in which, in contrast to nidifugous birds, the period of embryonic development is comparatively short and the reserve of nutrient yolk in the egg is limited. For this reason, the hatchlings are born helpless. They are blind, and their musculature is weak. The body, which is naked or covered with sparse down, has an inconstant temperature. Nidicolous birds remain in the nest for a long time, where they are kept warm and fed by the parents. Nidicolae include Pelicaniformes, Columbiformes, Cuculiformes, Psittaci-formes, Cypseliformes, Coraciiformes, Pici, and Passeriformes.
Some birds, such as owls and Falconiformes, are intermediate between nidicolous and nidifugous birds. The nestlings are born with a dense down and, in Falconiformes, with vision. The nidifugous type of development may be considered primary in birds, because it resembles reptilian development more closely than does nidicolous development.