Heron Rookery Survey
The refuge collected information on Great Blue heron nests from 1954-2006. Annually the refuge conducted a survey to determine the number of active nests within some of the rookeries that occur on the Duck River Unit. All active nests were counted during one visit that usually occurred in late May. This data was used to establish long-term trends.
The Grassy Lake Rookery was once the third largest rookery in the state. The number of nests has ranged from over 600 in the early 1990's to a low of 25 in 1976. The last survey done in 2006 only counted 6 nests as the bald cypress trees in which they nested had mostly died out. It is not felt that this decline has resulted in a local population decrease but just a shift in nesting locations. Within the last several years other great blue heron rookeries have been established on the Duck River Unit, primarily on islands on Kentucky Lake