Sea surface temperature constrains wedge-tailed shearwater foraging success within breeding seasons

Abstract

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.

Impact of El Niño on the foraging behavior of female northern elephant seals

“…As sea surface temperature and the position of frontal systems change as a result of El Niño effects in the North Pacific Ocean, the oceanographic features that help to determine prey patch characteristics may be altered with resulting impacts on foraging economics. A previous investigation on seabirds found that forage resource availability fluctuated daily in association with fine scale variation in SST during El Niño (Peck et al 2004). The migration tracks of the 2 female elephant seals with the greatest foraging success ('Wav' and 'Sun') covered areas associated with the meandering transition zone chlorophyll front (TZCF).…”

Effect of El Niño on the diet of a specialist seabird, Sula nebouxii, in the warm eastern tropical Pacific

“…Devney et al 2009, Oro et al 2010. These associations have been attributed to fine-scale variations in sea-surface temperature that force shifts in the abundance of prey through a bottom-up process (Barber & Chavez 1983) or affect the behaviour or physiology of prey and their distribution in the water column (Peck et al 2004). Oceanographic anomalies may influence the demography of seabirds, not only through changes in prey availability, but also through changes in the physical scenario in which foraging, breeding and offspring development occur (Clark et al 1990), suggesting that effects of climate on seabird populations may involve multiple variables (Abraham & Sydeman 2004, Thayer & Sydeman 2007.…”

Ocean control of the breeding regime of the sooty tern in the southwest Indian Ocean

“…Anderson et al 1982, Cruz & Cruz 1990. Similarly, the abundance and availability of prey have often been related to fluctuation of SST driven by climate variability (Hyrenbach & Veit 2003, Peck et al 2004, such as the seasonal cycle (Spear et al 2001). In tropical areas, surface enrichment in chlorophyll leads to a higher abundance of zooplankton and flying fish (Piontkovki and Williams 1995), which are largely preyed on by tropical birds.…”