Processes that underlie impacts of global warming on marine organisms at upper trophic levels are largely unknown. Long-term studies of seabirds indicate that inter-annual decreases in fledging success are correlated with El Niño years, when sea surface temperatures (SSTs) are above long-term averages. These studies propose that seasonal processes are most likely responsible. To date, no work has focused on the potential impacts of elevated SSTs on seabird reproduction at finer time scales, i.e. within a breeding season. We directly measured the influence of SST variability on foraging success in the wedge-tailed shearwater Puffinus pacificus within and among 3 breeding seasons at Heron Island in the southern Great Barrier Reef, Australia. We found that changes in foraging success (meal size and feed frequency) and chick growth were negatively correlated with daily variations in SST both within and among seasons. Our findings suggest that forage resource availability fluctuated daily in direct association with small-scale variation in SST. This is evidence that declines in seabird breeding success, previously coupled exclusively with large-scale El Niño conditions and processes, may also involve fine-scale mechanisms. Consequently, observed El Niño scale impacts may include season-specific outcomes of day-to-day trophic interactions that operate within all breeding seasons.

We examined divergence in foraging, provisioning and chick developmental patterns between wedge-tailed shearwaters Puffinus pacificus breeding at a temperate (Lord Howe Island) and sub-tropical (Heron Island) location. We aimed to evaluate the potential for different foraging environments to cause co-ordinated adaptive divergence in these characteristics. Adult foraging and provisioning behaviour differed significantly between locations, reflecting lower near-colony resource availability at Heron Island. Chick developmental patterns also differed significantly between locations. Overall, chicks at Lord Howe Island grew faster and had greater skeletal growth per gram of food delivered. In contrast, chicks at Heron Island exhibited greater body mass gains per gram of food delivered. Based on previously observed physiological or facultative responses to changes in provisioning rates in seabirds and long-term patterns of primary productivity at each location, we propose these developmental differences reflect colony-specific physiological adaptations to differences in long-term provisioning rates. If so, our results suggest co-ordinated environmentally determined divergent coevolution of chick and adult life-history parameters between these 2 locations.KEY WORDS: Procellariiform · Shearwater · Chick development · Co-ordinated divergence · Foraging behaviour · AdaptationResale or republication not permitted without written consent of the publisher

Mechanisms that drive sex‐specific foraging behaviour in seabirds are not fully understood. In some cases, sexual‐size dimorphism has been implicated. However, recent empirical work indicates that foraging behaviour may also differ between sexes of monomorphic seabird taxa. We simultaneously examined sex‐specific differences in adult foraging behaviour, chick provisioning rates and maximum dive‐depths in a monomorphic seabird, the wedge‐tailed shearwater Puffinus pacificus. We found significant divergence between sexes. Mean foraging trip length was longer, provisioning rate lower and mean maximum dive‐depth shallower in females. We found no evidence of divergence in foraging behaviour due to condition‐dependant increases in self‐provisioning by females, or differences in the nest attendance patterns of each sex. In addition, chick body condition did not influence meal mass or trip length differently in one or other sex. Consistent with results obtained for dimorphic species we suggest that inter‐sexual competition at the foraging grounds provides the most parsimonious explanation for the sex‐specific differences observed in this monomorphic species. Based on our findings we believe this possibility warrants further critical investigation.

Peck, D. R. and Congdon, B. C. 2004. Reconciling historical processes and population structure in the sooty tern Sterna fuscata. Á/ J. Avian Biol. 35: 327 Á/335.To test the influence of past vicariant events on population genetic structure of the sooty tern Sterna fuscata , we examined sequence variation in the mitochondrial control region of individuals from the Indo-Pacific and Atlantic Oceans. Our analyses indicate a rapid population expansion at a global scale during the last 100 000 years, consistent with global recolonisation during the interstade following the Pleistocene glacial maxima (125 000 Á/175 000 years bp). We estimate islands of the Great Barrier Reef and Coral Sea were colonised no more than 16 000 years ago, most likely in association with the appearance of new breeding habitat following the final Pleistocene glacial retreat (19 000 Á/22 000 years bp). Our results suggest that ice sheets linked to major glacial events not only impact genetic structuring in temperate seabirds, but that sea level changes in the tropics associated with these same events have also significantly impacted contemporary genetic structuring in tropical seabird species.

Feral cat Felis catus predation on seabirds has been well documented; however, details regarding shifts in feral cat diet in relation to seabird availability, seabird predation rate and impact on seabird population dynamics are scarce. Here, we present data documenting a seasonal shift in feral cat diet at Juan de Nova Island, Mozambique Channel. We also quantify sooty tern Sterna fuscata predation by feral cats and examine the impact on sooty terns over both the short term (by removing individual cats from sub-colonies) and over the longer term by highlighting their influence on population growth rate (l) using a deterministic matrix model. Cat diet shifted dramatically from insects, rats and mice outside the tern breeding season to primarily terns when terns were breeding. The predation rate of sooty terns at Juan de Nova was estimated at 5.94 terns cat À1 day À1 , with a proportion of these (22%) being killed without being consumed ('surplus kills'). When only one cat was removed from each sub-colony, tern predation declined tenfold in the short term. From our matrix model, the annual growth rate for sooty terns was 1.01 in the absence of cat predation. It remained above one until a predation impact equivalent to approximately three times the estimated cat density (12.04 per km 2 ) was incorporated. Our results demonstrate that cats preferentially predate and have an impact on breeding sooty terns at Juan de Nova, and that an increase in cat density could lead to negative effects on population growth, despite the large breeding tern population.