Audubon Canyon Ranch (ACR) has been monitoring nesting Great Blue Herons (Ardea herodias), Great Egrets (Ardea alba) and Snowy Egrets (Egretta thula) in Picher Canyon since 1967. This colony site is located at the Martin Griffin Preserve, on the northeast side of the Bolinas Lagoon, near Bolinas, CA (Figure 1). ACR has also been monitoring nesting herons and egrets at the Bolinas colony site, at the base of the Francisco Mesa adjacent to the Bolinas Channel, since 1990.