Type of Document:
In 2015, as in other years, Great Blue Herons, Great Egrets, Snowy Egrets, and Black-crowned Night-Herons nested on West Marin Island (none on East Marin Island); however, all of the nesting Snowy Egrets and Black-crowned Night-Herons abandoned the site before completing the nesting cycle and, by 2 June 2015, only five Great Blue Heron nests and 26 Great Egret nests remained active (Kelly et al. 2015). The cause of the 2015 abandonments is unknown. In 2016, we found no evidence of successful nesting by herons or egrets on West Marin Island. However, seven Great Blue Heron nests were established on East Marin Island and a few of those nests were apparently successful in fledging young. In this report, we present our detailed observations of heron and egret nesting activity on the Marin Islands in 2016.
Audubon Canyon Ranch (ACR) has been monitoring the number of nesting herons and egrets at Marin Islands since 1979, and the annual reproductive success of Great Egrets and Great Blue Herons there since 1993. Nests are monitored annually, during repeated visits, from viewing positions on East Marin Island and by boat. This work is part of an ongoing, regional study of heron and egret colonies in the northern San Francisco Bay area (see References Cited).
Web Page Link:
Kelly, J. P., and B. Fischer. 2017. Heron and Egret Monitoring Results at Marin Islands National Wildlife Refuge: 2016 Nesting Season. Report to the San Pablo Bay National Wildlife Refuge. ACR Technical Report 90-3-40 © January 2017. Audubon Canyon Ranch, Cypress Grove Research Center, P. O. Box 808, Marshall, CA 94940