The Collaborative International Dictionary
Nidification \Nid`i*fi*ca"tion\, n. [Cf. F. nidification.] The act or process of building a nest.
Douglas Harper's Etymology Dictionary
"nest-building," 1650s, from nidify, from Latin nidus "a nest" (see nest (n.)) + -ify.
n. The building of a nest.