Presentation Abstract

Title: Use of artificial floating islands for nesting and refuge by the endangered California clapper rail.
Session Title: "Ecology, Conservation and Management of Birds"
Session Number: 44
Session Time: Monday, Oct 15, 2012, 1:00 PM - 5:00 PM
Presentation Time: Monday, Oct 15, 2012, 1:00 PM - 5:00 PM
Presentation Number: 22
Author(s): Cory T. Overton1, Thuy-Vy Bui2, Michael Casazza1, John Takekawa2, 1US Geological Survey, Dixon, CA, 2US Geological Survey, Vallejo, CA, Contact: coverton@usgs.gov
Abstract Body: Projected changes in sea-level indicate increasing risks to obligate tidal marsh species such as the endangered California clapper rail (Rallus longirostris obsoletus). Increased inundation of primary habitats threatens to lower both survival and reproduction through intermittent loss of refuge cover and flooding of nesting substrate. We provided artificial refuge cover and nesting substrate for California clapper rails using floating islands and assessed use with respect to tidal inundation patterns and availability of natural refuge cover. Artificial refuge islands (1.5x2 m) were deployed at 10 locations in Arrowhead Marsh in Oakland, CA during the winter of 2010-11 and 2011-12. Artificial nesting islands (0.5x0.66 m) were deployed at 25 locations within each of 5 marshes in South San Francisco Bay from February 2012 to August 2012. All islands were constructed of recycled plastic materials with woven palm screens attached to rigid support poles providing cover. Waterproof, digital cameras mounted on each island recorded time elapsed images to monitor use. Nearly three million photos showed that rails regularly occupied all of the artificial refuge islands. Use of refuge islands by clapper rails increased slowly with tide level until tides reached 1.5 meters. Above 1.5 meters the odds of island use were 23 times the odds of use below 1.5 meters. Island use was also strongly diurnal. Odds of daytime use were 320 times the odds of use during the evening. Artificial nesting islands were used both for refuge during tidal inundation and as nesting substrate. Our results suggest that clapper rails in San Francisco Bay are strongly attracted to artificial habitats which provide protection from tidal inundation. Artificial islands for California clapper rails may be a timely and effective method for providing relief from adverse impacts of limited refuge and nesting habitat and could inform future habitat management under sea level rise scenarios.



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