Removing invasive mice will benefit stormpetrels through reduced owl predation

By Nadav Nur

We used Point Blue’s long-term data to examine the complex relationship between house mice, burrowing owls, and ashy storm-petrels on the Farallon Islands National Wildlife Refuge and to provide a quantitative estimate of the anticipated benefit to ashy storm-petrels from a proposed house mouse eradication project.

Surveys by Point Blue biologists revealed a strongly seasonal pattern among the three species. Owls arrive at the refuge in the fall when mice are super-abundant as prey. But the mouse population crashes mid-winter each year due to seasonal rains and cold temperatures. This causes the owls to switch to preying upon storm-petrels which begin to return to the refuge at this time to breed. As a result, owl predation on storm-petrels is highest in late winter.

Analysis of storm-petrel capture/recapture data revealed a declining population trend in recent years and showed that annual adult survival is inversely related to owl abundance, especially during winter.

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Read the original article in Ecosphere.