Seabird Restoration:
Restore Seabirds to Santa Cruz Island
Background
The goal of restoration efforts on Scorpion rock, Orizaba rock, and within sea
caves surrounding Santa Cruz Island (SCI) is to restore seabird habitat by
removing non-native vegetation, installing artificial nest boxes, and reducing
human disturbance. Eggshell thinning caused by elevated levels of DDTs was
documented in the eggs of Ashy storm petrels, California brown pelicans,
Cassin’s auklets, double-crested cormorants, and Xantus’s murrelets in the
Southern California Bight.
Restoration actions at Orizaba Rock and surrounding sea caves involve installing
artificial nest sites for Ashy storm-petrels to prevent or reduce impacts from
avian predation or human disturbance. Ashy storm-petrels are rare and endemic
to California and northwestern Baja California, with a world population of less
than 10,000 individuals. At SCI, certain offshore rocks (notably Orizaba Rock)
and sea caves continue to host small nesting colonies. Nests are primarily
found in rock crevices, under small rocks or boulders, under driftwood, or in
open sites along cave walls. Much of the habitat available to storm-petrels is
thus extremely fragile. Small colony sizes and fragile habitats make Ashy
storm-petrels highly susceptible to natural or human impacts. Recorded
vocalizations were used to attract Ashy storm-petrels to the artificial nests
on Orizaba Rock.
Scorpion Rock is a small islet located off the northeast coast of SCI.
Restoration efforts on Scorpion Rock are focused on nesting Cassin’s auklets.
Natural Cassin’s auklet burrows are present in relatively small numbers on the
rock, mainly due to the scarce vegetation and associated high rate of soil
erosion. Restoration actions on Scorpion Rock will improve and enhance existing
natural habitat for Cassin's auklets by restoring native vegetation,
stabilizing soil to minimize erosion, and eradicating invasive, nonnative
vegetation. Nest boxes were installed to provide a stable and secure nesting
area for Cassin's auklets.
(Scorpion Rock Film)
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Biological Monitoring
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Biologists continued nest monitoring for Ashy storm-petrels at five locations
on Santa Cruz Island including Orizaba Rock, and four sea caves.
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Biologists continued monitoring and banding of Cassin’s auklets on Scorpion
Rock and Prince Island.
Habitat Restoration
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Biologists and volunteers planted 3,000 plants on Scorpion Rock in 2009 to
augment the 2008 ouplanting effort. Site work such as removing non-native
plants, soil stabilization, and vegetation mapping have been ongoing since
2007.
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Fifty artificial nests sites were installed on Orizaba Rock and in Cavern Point
Caves for Ashy storm-petrels and have hosted successful breeding pairs.
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An audio system has been placed on Orizaba Rock to attract seabirds for the
past two breeding seasons, and audio-visual assessments will begin in 2010.
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