| Summary: | Populations of nocturnal burrow-nesting seabirds are notoriously difficult to measure because of their cryptic behavior at remote breeding sites. However, there is an urgent need to identify factors that influence recovery of these populations, because of the increasing number of introduced-predator eradication projects whose ultimate goal is to facilitate seabird and, thus, ecosystem recovery. We asked whether the relative status of nocturnal burrow-nesting seabirds across the Aleutian Islands, Alaskainferred from levels of vocal activity collected with automated acoustic recording devices-can be explained in terms of ecological factors such as time since eradication, island size, and distance to source population. We deployed a total of 19 acoustic recorders on six islands during 2008–2010. Overall nocturnal call activity (mean number of calls night-1 ± SE) was high (493 ±287) where predators were never introduced, low (0.3 ± 0.1) where introduced rats were present, and intermediate (29 ± 18) where introduced predators have been eradicated. Using an information-theoretic approach, we found support for multiple factors as an explanation for the call activity of Leach's Storm-Petrels (Oceanodroma leucorhoa), Fork-tailed Storm-Petrels (O. furcata), and Ancient Murrelets (Synthliboramphus antiquus). Specifically, we conclude that although recovery of nocturnal burrow-nesting seabird populations in the Aleutians is not straightforward, the presence of nearby “predator refugia” may maximize the probability of seabird recovery and can be used when prioritizing islands for eradication programs.
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