The Black-headed Gull breeds on the ground in dense colonies, and the colony itself is the species' most important protection against predators during breeding.
Site: on islands, in reedbeds and on floating vegetation in lakes and wetlands, often in the nutrient-rich waters of lowland landscapes.
Construction: a simple nest of reeds and plant material placed close beside the neighbours', sometimes hundreds of pairs in the same colony.
Protective value: the colony provides protection for other species too, such as grebes and dabbling ducks, which readily breed within the Black-headed Gull colony, and the female normally lays 3 eggs.