The Distribution, Reproductive Success, and Habitat Characteristics of Heron and Egret Breeding Colonies in the San Francisco Bay Area

In 1991, inventories were conducted at 55 heron and egret breeding colony sites in the San Francisco Bay area; 44 of these were monitored with multiple visits. Eight colony sites were visited 10 or more times during the season. The breeding colonies included 45 Great Blue Heron (Ardea herodias), 17...

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Bibliographic Details
Published in:Colonial waterbirds 1993-01, Vol.16 (1), p.18-27
Main Authors: Kelly, John P., Pratt, Helen M., Greene, Philip L.
Format: Article
Language:English
Subjects:
Animal nesting
Ardea herodias
Ardeidae
Bird nesting
Brackish
Breeding
Breeding sites
Egretta thula
Freshwater
Marshes
Nesting sites
Nycticorax nycticorax
Productivity
Salt marshes
Wetlands
Wildlife habitats
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Summary:In 1991, inventories were conducted at 55 heron and egret breeding colony sites in the San Francisco Bay area; 44 of these were monitored with multiple visits. Eight colony sites were visited 10 or more times during the season. The breeding colonies included 45 Great Blue Heron (Ardea herodias), 17 Great Egret (Casmerodius albus), seven Snowy Egret (Egretta thula), and 11 Black-crowned Night-Heron (Nycticorax nycticorax) colonies. Isolated islands in central San Francisco Bay provided regionally important nesting habitat for Snowy Egrets and Black-crowned Night-Herons. We found no relationship between the extent of tidal marsh habitat within major subregions of the Bay and the distributions of nesting ardeids. However, a high concentration of nesting Great Egrets in Suisun Bay coincided with the most biologically productive waters in the San Francisco Bay estuary. Great Blue Heron colonies were well dispersed throughout the area, especially along the outer Pacific Coast and in the Russian River/Laguna de Santa Rosa drainage. Overall prefledging (4-7 weeks old) brood size among successful Great Blue Heron nests was 1.93 ± 0.61 (SD) young per nest, with no difference between "interior" colonies that were ≥ 10 km from saltwater or brackish feeding areas and colonies closer to the coast.
ISSN:0738-6028
DOI:10.2307/1521552