Western Screech-Owl Pen and Ink? Tony Angell 1974? Collection of the artist? A sleepy male screech-owl comes to the entrance of his roosting hollow. In addition to sleeping and roosting, hollows are used for feeding and caching food. They also shelter the birds from the elements and from larger owls, hawks, and mobbing birds. In addition to natural hollows, screech-owl cavity sources include abandoned woodpecker or flicker excavations, bird boxes, and suitable crevices in buildings. Other Stanford cavity nesters, including the American Kestrel, Western Bluebird, Ash-throated Flycatcher and Chestnut-backed Chickadee, are the focus of a three-year initiative to halt the decline in area's native cavity nesting birds.