The herons are a widespread family with a cosmopolitan distribution. They exist on all continents except Antarctica, and are present in most habitats except the coldest extremes of the Arctic, extremely high mountains and the driest deserts. Almost all species are associated with water, they are essentially non-swimming waterbirds that feed on the margins of lakes, rivers, swamps, ponds and the sea. They are predominantly found in lowland areas, although some species live in alpine areas, and the majority of species occur in the tropics.
The herons are a highly mobile family, with most species being at least partially migratory. Some species are partially migratory, for example the grey heron, which is mostly sedentary in Britain but mostly migratory in Scandinavia. Birds are particularly inclined to disperse widely after breeding but before the annual migration where the species is colonial, searching out new feeding areas and reducing the pressures on feeding grounds near the colony. The migration typically occurs at night, usually as individuals or in small groups.