| Summary: | Numerous declines and extinctions of native wildlife populations have been caused by the introduction of non-native plants and animals to islands (Huyser et al. 2000, Marinez-Gomez and Jacobsen 2004). Various members of the Order Rodentia have contributed to this world wide phenomenon (Cuthbert and Hilton 2004). Many rodents are omnivores and members of the taxa have been known to feed on bird eggs, birds, insects, ant eggs, meat, bacon, cannibalism, lizards, carrion, slugs, and mammal bones (Landry 1970). Previous studies found house mice (Mus musculus) diets to be omnivorous but the diet varied with location of the study (primarily invertebrates in cultivated regions of North America, Whitaker 1966; invertebrates, vegetation, and vertebrate material on sub-Antarctic Islands, Copson 1986; and seasonal change with food availability on South Atlantic Islands, Jones et al. 2003). House mice have also been found to damage eggs (Maxon and Oring 1978) and feed on live chicks of Tristan Albatross (Diomedea dabbenena) and Atlantic Petrel (Pterodroma incerta) (Cuthbert and Hilton 2004). Egg size probably does not provide protection against mouse predation as Blight and Ryder (1999) found that Peromyscus consumed the eggs of Rhinoceros Auklets (Cerorhinca monocerata). In addition to direct affects on seabirds through predation, house mice have been found to alter the plant and invertebrate communities on islands and result in greater effects than just through predation (Chown and Smith 1993, Smith et al. 2002). Mice may also indirectly affect seabird populations by supporting winter populations of predators which switch their diet to the seabirds when seabirds become available at nesting colonies in the spring (Drost 1989). Southeast Farallon Island, in the Farallon Island archipelago, is located 32 km southwest of Point Reyes, California, USA. This important seabird breeding colony in western North America, includes the world’s largest populations of breeding Ashy Storm- Petrels (Oceanodoma homochroa), Brant’s ...
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