Changes in the world's oceans have altered nutrient flow, and affected the viability of predator populations when prey species become unavailable. These changes are integrated into the tissues of apex predators over space and time and can be quantified using stable isotopes in the inert feathers of historical and contemporary avian specimens. We measured δ¹³C and δ¹⁵N values in Flesh-footed Shearwaters (Puffinus carneipes) from Western and South Australia from 1936–2011. The Flesh-footed Shearwaters more than doubled their trophic niche (from 3.91 ± 1.37 ‰² to 10.00 ± 1.79 ‰²), and dropped an entire trophic level in 75 years (predicted δ¹⁵N decreased from +16.9 ‰ to + 13.5 ‰, and δ¹³C from −16.9 ‰ to −17.9 ‰) – the largest change in δ¹⁵N yet reported in any marine bird, suggesting a relatively rapid shift in the composition of the Indian Ocean food web, or changes in baseline δ¹³C and δ¹⁵N values. A stronger El Niño-Southern Oscillation results in a weaker Leeuwin Current in Western Australia, and decreased Flesh-footed Shearwater δ¹³C and δ¹⁵N. Current climate forecasts predict this trend to continue, leading to increased oceanic ‘tropicalization' and potentially competition between Flesh-footed Shearwaters and more tropical sympatric species with expanding ranges. Flesh-footed Shearwater populations are declining, and current conservation measures aimed primarily at bycatch mitigation are not restoring populations. Widespread shifts in foraging, as shown here, may explain some of the reported decline. An improved understanding and ability to mitigate the impacts of global climactic changes is therefore critical to the long-term sustainability of this declining species.

Item Type:	Refereed Article
Keywords:	stable isotope analysis, overfishing, El Nino Southern Oscillation
Research Division:	Biological Sciences
Research Group:	Ecology
Research Field:	Marine and Estuarine Ecology (incl. Marine Ichthyology)
Objective Division:	Environment
Objective Group:	Flora, Fauna and Biodiversity
Objective Field:	Marine Flora, Fauna and Biodiversity
Author:	Lavers, JL (Dr Jennifer Lavers)
ID Code:	90741
Year Published:	2014
Web of Science® Times Cited:	9
Deposited By:	IMAS Research and Education Centre
Deposited On:	2014-04-23
Last Modified:	2015-03-27
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