The atlas of heronies summarizes continuing efforts by Audubon Canyon Ranch and the San Francisco Bay Bird Observatory to monitor colonially nesting herons and egrets in the central coastal region of California surrounding the San Francisco estuary. The methods used provide for the intensive regional monitoring of nesting distributions, nest survivorship, productivity of successful nests, nesting habitat characteristics, and intraseasonal timing. The analysis focuses on comparisons of heron and egret nesting performance among nine major wetland subregions from 1991-2005.

We evaluated landscape associations related to heron and egret colony site selection and the productivity of successful great blue heron (Ardea herodias) and great egret (Ardea alba) nests. The study was based on annual observations (1991–2005) at 45 colony sites known to be active within 10 km of historic tidal marshes of northern San Francisco Bay.

Landscape influences on the quality of heron and egret colony sites