The Mediterranean Gull breeds in colonies on islands, readily embedded within colonies of Black-headed Gull, whose dense and noisy company provides collective protection from predators. The female normally lays 2–3 eggs in a shallow nest cup of plant material. Both parents take part in incubation and in the care of the young. The species' readiness to breed in Black-headed Gull colonies means that new occurrences often arise precisely where such colonies exist.