A heronry, sometimes called a heron rookery, is a breeding ground for herons.
Notable heronries
Although their breeding territories are often on more protected small islands in lakes or retention ponds, herons breed in heronries (or also called rookeries, especially since other birds join them like spoonbills, storks, and cormorants). Some of the notable heronries are:
The Florida Everglades in south Florida, of the United States. Thousands of birds, including herons, egrets, spoonbills, and storks, nest in mangroves (genus Rhizophora).
Media related to Heronries at Wikimedia Commons