How do male sticklebacks build their nests?

Male sticklebacks, which belong to the order Gasterosteiformes, exhibit highly ritualized reproductive behaviour during the spring breeding season.

To build a nest, the male gathers plant materials and cements them together using threadlike, mucous secretions produced by his kidneys. Once the structure is complete, the male—whose body has taken on vibrant colors such as red, yellow-orange, or black—coaxes a female into the nest to lay her eggs. After fertilizing the eggs, the male assumes the role of guardian, aggressively defending the nest and aerating the eggs by fanning them with his pectoral fins until they hatch.12