1. Remaining in the nest for some time after hatching.
2. Sharing the nest of another kind of animal.
Usually, nidicolous animals are altricial (helpless when born).
The second definition is used in reference to parasites, for example nidicolous ticks that live in or near the nests of their hosts.
Etymology: Latin nidus, nest + colere, to inhabit.
The opposite of nidicolous is nidifugous - able to leave the nest very quickly.