The Great Blue Heron nesting colony at DeSilva Island, in Marin County, California, is one of many colony sites that are monitored by Audubon Canyon Ranch (ACR) as part of its North Bay Heron and Egret Project. The Project was initiated in 1990 and reflects an ongoing effort to monitor the status of colonially nesting herons and egrets throughout five counties in the northern San Francisco Bay region. The primary goal of the Heron and Egret Project is to develop and apply current and historical information on status of herons and egrets to wetland conservation concerns in the San Francisco Bay area. Specifically, the project focuses on monitoring local and regional trends in nesting abundance and reproductive performance (Kelly et al. 2006, 2007). A brief summary of colony site locations and results is posted online at https://egret.org/googleearthheronries.