The male stickleback's belly turns red at the start of the breeding season in spring. Normally the belly of this small fish is silver-colored, the rest of it varying from brown to green. But when the time comes for him to mate he becomes very active in attracting females with his bright new color.
In building the home and rearing the family the male stickleback performs many of the functions usually associated with a female fish. He chooses the place for the nest, collects the stems of various aquatic plants and binds them together using a threadlike web secreted from his kidney.
Once the female has been enticed into his nest, she will lay her eggs and depart, leaving him on guard. He watches over the eggs with great care and even looks after the baby fish.