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Restoring the Native Plant Community on Scorpion Rock to Enhance Nesting Habitat for Burrow- and Shrub-Nesting Seabirds in the California Channel Islands

Released: 2016
Adams, J., D. Mazurkiewicz, A.A. Yamagiwa, J.A. Howard, C. Carter, A. L. Harvey, A. Little. 2016. Restoring the Native Plant Community on Scorpion Rock to Enhance Nesting Habitat for Burrow and Shrub-Nesting Seabirds in the California Channel Islands. 9th California Islands Symposium, Ventura, CA, 3-7 October, 2016.

Invasive, non-native plant species introduced to California’s Channel Islands can affect seabird nesting habitat quality and impose threats to population growth and recovery. Scorpion Rock, located off the northeast end of Santa Cruz Island in Channel Islands National Park, is an important seabird nesting and roosting location. A legacy of human use and visitation allowed the spread of invasive, non-native plant species on Santa Cruz Islands and adjacent Scorpion Rock. The altered vegetative cover likely contributed to decreased abundance and quality of nesting habitat for burrow-nesting Cassin’s Auklet (Ptychoramphus aleuticus australis) and crevice- and shrub-nesting Scripps’s Murrelet (Synthliboramphus scrippsi). The removal and control of non-native vegetation and outplanting of >9,000 native plants during 2008 – 2014 has dramatically changed the landscape of Scorpion Rock. Vegetative cover changed from 94% invasive weeds (6 exotic species, mostly crystalline iceplant [Mesembryanthimum crystallinum]) in 2008 to 10% invasive weeds (4 – 5 exotic species) in 2014. During 2012 – 2014, we recorded little change in relative cover of M. crystallinum; vegetative and desiccated cover combined were annually variable, but this species has remained at low coverage since 2011 (2 – 13% cover). Cheeseweed (Malva parviflora) and nettle-leaf goosefoot (Chenopodium murale) remained virtually undetectable at <1% cover. Native plant richness included 6 species in 2008, and after reaching maximum richness in 2012 (21 species), has shown initial biodiversity stabilization (19 spp. in 2013, 17 spp. in 2014). Percent cover of native plant species reached a maximum in 2013 (66%) with an overall leveling-off trend since 2011 (percent cover remained consistent at ~60% cover). Native percent cover during 2012 – 2014 was dominated by Giant Coreopsis (Leptosyne gigantea; 27 to 43% cover), Alklai Heath (Frankenia salina; 3% cover), California Sage (Artemesia californica; 3 to 4% cover) and Brewer’s Saltbush (Atriplex lentiformis; 4 to 14% cover). Removal of non-native, invasive vegetation and the restoration of a native perennial Coastal Sage Scrub community on Scorpion Rock is helping to provide better soil structure, nesting conditions, and cover for burrow- and shrub-nesting nesting seabirds and new habitat for invertebrates and passerines. Evaluation of weed control methods and the development of remote-site-restoration-techniques has benefitted other habitat restoration projects on the Channel Islands.

This product is associated with the following project:
Research and Restoration in the California Channel Islands

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