Females move among the advertising males with thin, up-stretched necks. As a female approaches a group of males (center), there is a sudden increase in displays.
After they pair up the male gathers nesting material while the female builds the nest. Their guano glues it together. Both the male and female defend their nest site from interlopers. When a nest exchange is made the eggs are turned by the new sitter. Incubation (28-31 days) is carried out by both parents. Care is taken during a nest exchange because Western Gulls are waiting for their chance to snatch an egg or a nestling. Rarely are eggs left unattended.