Habitat Use, Behavior, and Morphology of Herons and Egrets in Elkhorn Slough, California
HABITAT USE, BEHAVIOR, AND MORPHOLOGY OF HERONS AND EGRETS IN ELKHORN SLOUGH, CALIFORNIA I \ A thesis submitted to the faculty of San Francisco State University in partial fulfillment of the requirements for the degree Master of Science in Marine Science / by Pamela Elaine Byrnes ~' San Francisco, California December, 1997 Habitat Use, Behavior, and Morphology of Herons and Egrets in Elkhorn Slough, California. Pamela Elaine Byrnes San Francisco State University 1997 Great Blue Heron (Ardea herodias), Great Egret (Ardea alba), and Snowy Egret (Egretta thula) were surveyed from January to August 1996 in Elkhorn Slough and surrounding wetlands. Ninety-one wetland sites were surveyed 68 to 72 times during daylight hours throughout the tidal range. Hierarchical loglinear analyses indicated that ardeid occurrence at wetland sites was dependent upon time of day, tide level, and area. Logistic regression analyses identified three environmental cHaracteristics associated with the presence of Great Blue Herons (channels/ditches, pickleweed flats, ponded water) and three characteristics associated with the presence of Great E~rets and Snowy Egrets (pickleweed, roosting structures, water depth). Three additional characteristic were associated with Snowy Egrets (mud, mid-tides,and late daylight hours). I certify that the Abstract is a correct representation of the content of this thesis. ------- ,.-----. .1 I. \Jmni' I, Nlt!l!i/'f'i, 11 0/. /71;- (Chair, Thesis Committee) ) (Date) ACKNOWLEDGMENTS l thank my advisory committee; Dr. James T. Harvey, Dr. Shannon M. Bros, and Dr. Luis F. Baptista for their encouragement, guidance, and skill at sharing their knowledge. Thanks to the Moss Landing Marine Laboratories and San Francisco State University staff, especially Sheila Baldridge, Gail Johnston, Lynn McMasters, and Kathleen Baker.
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