The Effects of Mammalian Predators on a Southern Oregon Colony of Leach's Storm- Petrels (Oceanodroma leucorhoa)

• Main Author: Pollard, Anne M. (Anne Marie), 1984-
• Format: Thesis
• Language: English
• Published: University of Oregon 2008
• Subjects: Burrows; Oceanodroma leucorhoa
• Online Access: http://hdl.handle.net/1794/8712

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. 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. Committeein Charge: Dr. Alan Shanks, Chair; Dr. Jan Hodder; Dr. Rob Suryan