Breeding biology and consequences of nest site use in fork-tailed storm-petrels (Oceanodroma furcata) recovering from fox predation in the Aleutian Islands, Alaska

Seabirds forage in the marine environment but nest on land and therefore may be affected by changes in both marine and terrestrial habitats. The purpose of my study was to explore two important aspects of seabird conservation, variation in prey supply in the marine environment and the introduction of mammalian predators to breeding colonies, using a widespread Pacific seabird, the Fork-tailed Storm-Petrel (Oceanodroma furcata).; My first goal was to examine variation in Fork-tailed Storm-Petrel reproductive parameters over a two-year period. I found significant annual or seasonal variation in a number of parameters. Hatch date, egg volume, chick survival, chick condition, feeding rate, and food load all differed between years, while chick diet and adult condition varied across the season. Patterns of variation in several of these variables were consistent with those of other studies that linked seabird breeding biology to food availability and weather conditions. Although associations with prey supply were speculative, these results suggest that a number of Fork-tailed Storm-Petrel breeding parameters may potentially serve as useful indicators of changes in marine ecosystems.; My second goal was to investigate the potential reproductive consequences of changes from soil to rock nesting habitat due to introduced foxes in the Aleutian Islands. On an island recovering from fox predation where birds now nest in rock habitat rather than typical soil burrows, I examined the relationships between the amount of rock making up a nest, nest microclimate, and reproductive success. I found that nests with greater amounts of rock had lower chick survival and lower and more variable temperatures than nests with less rock. In addition, nest temperature was directly related to chick survival, with lower survival in colder nests. These results suggest that nesting in rock habitat in the absence of foxes may depress Fork-tailed Storm-Petrel reproductive success. Therefore, fox introductions in the Aleutian Islands may affect storm-petrel populations long after foxes are removed. This provides evidence for potential lasting effects of introduced predators on seabirds and island ecosystems.; This study has implications for the use of Fork-tailed Storm-Petrels as an indicator of changes in the northern Pacific Ocean, and also for the conservation and restoration of seabirds and island ecosystems through the removal of introduced predators.