Soon afterward, the females select their mates, but it is uncertain whether they are choosing the male or the nest site he is defending. Once mated, the male defends only the nest cavity, rather than a large area around it. This species is monogamous, but in some populations males are polygynous. European Starlings usually build their nests between late February and early March. The male begins building a nest before he has a mate, but the majority of the nest is built by the female, after the starlings have paired.
Females only build in the morning, and it usually takes two or three days to complete a nest.
During this time, males closely guard their mates to prevent other males from copulating with them. The cup of the nest is constructed of coarse grass, twigs, pine needles, rootlets, and straw and is lined with moss, feathers, wool, and fresh leaves. These leaves are replaced frequently and are believed to function as a natural insecticide or bactericide. The first eggs are laid around mid-March. Females lay one egg per day, and the average clutch contains four to seven eggs.