October 2017 - Battling invasive plants and restoring native ones might at first seem like a strange way of helping out an animal that spends the majority of its life at sea. Cassin’s auklets are known for their ability to “fly” underwater to depths of more than 100 feet in pursuit of small crustaceans. However, as seabirds, the time they spend on land is crucial. They come ashore primarily to breed and nest. Scorpion Rock, a small islet just off the coast of Santa Cruz Island in Channel Islands National Park, is one of their nesting locations.
Seabird nesting habitat is not easy to come by. It needs to be isolated and free of land predators like rats, foxes, and skunks. For Cassin’s auklets, good nesting habitat must also have lots of natural crevices. Alternatively, it must lend itself to the construction of nest burrows. Scorpion Rock was great for burrowing until crystalline iceplant, an invasive species, began driving out native vegetation and triggering soil erosion. Biologists monitoring nesting seabird colonies on the rock kept track as Cassin’s auklet numbers fell. Concerned, they began supplying the birds with artificial nest boxes in 2000. The iceplant, which covered 94% of the islet by 2008, remained problematic. Natural nest burrows were few, and the island’s only surviving native coreopsis plant could not shield the auklets from aerial predators such as barn owls, peregrine falcons and western gulls.