R.E. Johnson 1967 109 Great-blue Heron June 8 Stinson Beach, Marin Co., California (cont.) In grading a Zoo 107B Term Project by Richard Dehlinger, who studied the three species of Ardeidae in this same area [Bolinas Lagoon (north of Stinson Beach) and Audubon Canyon Ranch (east side of lagoon)] I note the following points: (1) Great Blue Herons (& Amer. Egrets) nest in colonies in the tops of second growth redwood trees at Audubon Canyon Ranch. (2) The lagoon is deeper at its northern end and greater concentrations of birds occur there. (3) Herons are relatively more common in the southern part of the lagoon than the other 2 species. (4) Herons (not others) fly (in small numbers) to feed in tide pools at low tide. (5) Herons (& Amer. Egrets) may also feed in adjacent marshy areas. (6) Herons begin feeding (arrive from nest area) earlier & remain later than American Egrets. (7) Heron feeds more slowly than Amer. Egret. (8) Heron is less efficient (fewer successful attempts (%) to catch fish) than Amer. Egret. (9) Herons (& Amer. Egrets) appear to feed on crabs in algae beds in the lagoon.