Type of Document:
A study of the breeding biology of Great Blue Herons (Ardea herodias) and Common Egrets (Casmerodius albus) was started in 1967 at Audubon Canyon Ranch, Marin County, California, where both species nest in the same heronry. I have reported on results of the first 2 years (1967, 1968) of the study (Pratt 1970). This paper presents findings on nesting success for 1969 and 1970 and adds data on clutch size for all 4 years. To facilitate comparison of nesting success with the 2 prior years, I include some previously published data.
There are few other studies of nesting success of these species. Vermeer (1969), Wilburn (1970), and Page (1970) reported on nesting success of the Great Blue Heron. Teal (1965) and Page (1970) did so for the Common Egret. Owen’s (1960) study of nesting success of the Gray Heron (Ardea cinerea) in England offers valuable comparative information.
Web Page Link:
Pratt, H. M. 1972. Nesting success of Common Egrets and Great Blue Herons in the San Francisco Bay region. Condor 74: 447-453.