Darren R. Peck

Elevated sea-surface temperature, reduced provisioning and reproductive failure of wedge-tailed shearwaters (Puffinus pacificus) in the southern Great Barrier Reef, Australia

During the 2002 austral summer abnormally high sea-surface temperatures (SST) occurred in the southern Great Barrier Reef (GBR), Australia. This phenomenon was accompanied by reduced provisioning, decreased growth rates and reproductive failure of wedge-tailed shearwaters in the region. In 2002, adults were unable to compensate for changes in either the availability and/or accessibility of forage-fish by increasing food loads or foraging rates. This is one of few studies to explicitly correlate decreases in chick provisioning with above-average annual variation in SST and is the first to do so for a tropical seabird species in the western Pacific. It adds to an increasing number of data sets identifying the potential negative impacts of increasing SST at upper-trophic levels. As SST continue to rise with global climate change, our results predict substantial detrimental effects on seabird populations of the GBR. This finding has important implications for both seabird and coral reef ecosystem management in the region. Our results also suggest that wedge-tailed shearwaters are sensitive indicators to changes in forage-fish availability/accessibility associated with SST variation that can be used to develop models of, and monitor for, these potential impacts.

Variation in egg-size in the Wedge-tailed Shearwater (Puffinus pacificus)

Abstract We assessed variation in the size of eggs of Wedge-tailed Shearwaters (Puffinus pacificus) within and between two colonies in eastern Australia. Eggs at Heron Island were significantly larger than at Lord Howe Island. We also found significant between-season variation in size of eggs at Heron Island, with larger eggs being laid in 2005 than 2006. Mean female size (as indicated by tarsal length) did not differ between the two colonies, or between seasons at Heron Island. However, as with other seabird species, larger females produced larger eggs. Overall, our results imply that facultative changes in female reproductive effort associated with changes in availability of resources are not the main cause of variation in egg-size in this species. The consistently smaller size of eggs for birds at Lord Howe Island compared with those from Heron Island suggests that obligate processes (e.g. natural selection) are more likely to be responsible.