New research from Point Blue Conservation Science shows the significant negative impact that invasive, non-native house mice on the Farallon Islands are having to the threatened ashy storm-petrel.
New research from Point Blue Conservation Science shows the significant negative impact that invasive, non-native house mice on the Farallon Islands are having to the threatened ashy storm-petrel. Original modeling by ecologists published today in the journal Ecosphere shows the potential impacts to the petrel’s population if mice are allowed to remain. The super-abundant mice encourage migrating burrowing owls to stay on the island, who later in the winter switch from eating mice to preying on the petrels.
The paper’s authors conclude that the owls are inhibiting population recovery for the ashy storm-petrel. Models show that if mice are removed from the island, reducing the presence of overwintering burrowing owls, the population of threatened petrels is projected to stabilize or potentially increase.
The ashy storm-petrel is a small, grayish-brown nocturnal seabird. Some experts estimate that there are only about 5,000-10,000 breeding ashy storm-petrels, with nearly half of the world’s population breeding on the South Farallon Islands. Because of its small population and the numerous threats it faces, it is listed as Endangered by the International Union for Conservation of Nature (IUCN) and a Species of Conservation Concern by federal and state agencies.
Burrowing owls regularly stop at the islands to rest during their fall migration and find a plentiful food source when invasive mice are at their seasonal population peak. Instead of continuing on their migration, several owls remain on the islands to feed on the mice. This keeps them on the island long past the natural time for them to move on to their wintering grounds. But the mouse population crashes each winter, forcing the owls to seek other prey. The owls then switch to preying on the rare ashy storm-petrels, which are just returning to begin their breeding cycle.
Read more at Point Blue Conservation Science