The Effects of Mammalian Predators on a Southern Oregon Colony of Leach's Storm- Petrels (Oceanodroma leucorhoa)
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Date
2008-12
Authors
Pollard, Anne M. (Anne Marie), 1984-
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Saddle Rock, with an estimated 86,300 birds, was the third largest colony of
Leach's Storm-petrels (Oceanodroma leucorhoa) in Oregon in 1988. This colony is
uniquely vulnerable to terrestrial predation due to its contiguity with the mainland during
low tides. In recent years, an increase in visitation of raccoons and river otters to Saddle
Rock has resulted in increased bird mortality. In 2007 I estimated predation rates ranging
from 0 to 59 birds per night, with predation occurring on 7 of 11 nights checked. 48% of
marked burrows were depredated throughout the season. In 2007 and 2008, I monitored
nesting density and burrow occupancy rates on Saddle Rock and compared these data
with those from nearby Hunters Island, a similarly sized colony. Saddle Rock now hosts
significantly lower densities than Hunters Island. Comparisons of recent Saddle Rock
data with those from 1979-1995 show a steep population decline.
Description
xii, 100 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.