Environmental extremes and biotic interactions facilitate depredation of endangered California Ridgway’s rail in a San Francisco Bay tidal marsh

California Fish and Game
By: , and 

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Abstract

On 23 December 2015 while performing a high tide population survey for endangered Ridgway’s rails (Rallus obsoletus obsoletus; formerly known as the California clapper rail) and other rail species at Arrowhead Marsh, Martin Luther King Jr. Regional Shoreline, Oakland, California, the authors observed a series of species interactions resulting in the predation of a Ridgway’s rail by an adult female peregrine falcon (Falco peregrinus). High tide surveys are performed during the highest tides of the year when tidal marsh vegetation at Arrowhead Marsh becomes inundated, concentrating the tidal marsh obligate species into the limited area of emergent vegetation remaining as refuge cover. Annual mean tide level (elevation referenced relative to mean lower low water) at Arrowhead Marsh is 1.10 m, mean higher high water is 2.04 m (NOAA National Ocean Service 2014) and the average elevation of the marsh surface is 1.60 m (Overton et al. 2014). Tidal conditions on the day of the survey were predicted to be 2.42 m. Observed tides at the nearby Alameda Island tide gauge were 8 cm higher than predicted due to a regional low-pressure system and warmer than average sea surface temperatures (NOAA National Ocean Service 2014). The approximately 80 cm deep inundation of the marsh plain was sufficient to completely submerge tidal marsh vegetation and effectively remove 90% of refugia habitats.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Environmental extremes and biotic interactions facilitate depredation of endangered California Ridgway’s rail in a San Francisco Bay tidal marsh
Series title California Fish and Game
Volume 102
Issue 4
Year Published 2016
Language English
Publisher California Department of Fish and Wildlife
Contributing office(s) Western Ecological Research Center
Description 5 p.
First page 157
Last page 161