Breeding occurs year round with a peak in November and December. The
nest is built of
guano on flat surfaces on offshore islands or remote headlands. There are up to three nests per square meter in high-density
colonies. The guanay cormorant lays two or three
eggs of approximately 63 × 40 mm in size. It feeds mainly on the
Peruvian anchoveta Engraulis ringens, and the
Peruvian silverside Odontesthes regia, which thrive in the cold
Humboldt Current. The guanay cormorant is the main producer of
guano.
Habitat loss and degradation and over-fishing have resulted in a steady decline of the population of about 30% from an estimated figure of three million birds in 1984. This species is listed as
near threatened by
IUCN. The bird's droppings were such an important source of fertilizer to the peoples of the Andes that it was protected by Inca rulers, who supposedly made disturbing the cormorants in any way punishable by death. The common name is an adaptation of the South American Spanish
guanae, a plural of the English equivalent
guano. ==References==