Using stable isotopes to assess climate-change impacts on migrations of prions (Aves:Procellariiformes)

Global warming has resulted in much faster and more pronounced ecological responses in marine than in terrestrial ecosystems. Yet most people are unaware of the dramatic changes going on in marine ecosystems because these are not readily observed from land. For example, oceanic copepod distributions have been found to be moving poleward 30 times faster than terrestrial animal distributions. Copepods are extremely abundant animals and are a key food resource in high latitude oceans. As ocean temperatures increase, high densities of large and nutritious copepods in cold waters are replaced by smaller and less nutritious species of warm-water copepods. Seabirds that specialize on a diet of large copepods may experience dramatic changes in the distribution of their main winter prey within the timescale of a single generation of these long-lived birds. This is potentially one of the most severe and rapid impacts of climate change on any vertebrates. Prions or "whale-birds" are southern oceans petrels that breed on subAntarctic islands. Prions are extremely abundant seabirds, and many of the largest colonies are on UK dependent territories such as South Georgia (for example over 20 million pairs on South Georgia) and Tristan da Cunha where colonies are protected by international conservation conventions. Due to their numerical abundance these small burrowing species are major consumers and therefore a change in their distribution or abundance has considerably knock-on effects for marine ecosystems. They have a highly specialized bill morphology evolved for filter feeding. Prion species differ in bill morphology, with the extent of dependence on copepods most pronounced in the broad-billed prion, and least in Antarctic prion and closely related blue petrel. We can infer the latitude where these birds spend the winter because in the southern hemisphere there is a very strong latitudinal gradient in carbon isotope ratios in marine foods. This enables tracking of wintering areas used by these birds. Feathers grown during the autumn/winter moult will have carbon isotope signatures that reflect the latitude where the birds were feeding while their feathers grew. Feathers collected from birds at their breeding sites can therefore be used to infer the main moulting/wintering regions visited by each individual bird. Analysis of historical samples (from museum collections) permits wintering latitudes used by these species in the past to be inferred in a similar way. We will validate the use of isotopes to infer wintering latitude by deploying small data loggers on a sample of prions to determine wintering areas using light level data recorded by the logger, a well established method already used on many seabirds, so we can measure isotopes in individuals with known wintering area. The key hypothesis we will test is that broad-billed prions have changed winter distribution in recent years to spend the austral winter at higher latitudes south of their breeding colonies, whereas in the past (from 150 years ago up until some time in the late 20th century) these birds migrated north from their breeding grounds to winter at lower latitudes in the southern hemisphere. We will also test the hypothesis that other prions show less poleward movement of winter areas (which we expect because they are less dependent on a copepod diet). Finally, we will test the hypothesis that poleward movement of broad-billed prions varies from year to year in relation to copepod distribution and density in each different year (data that are available for recent years from a Southern Ocean plankton database). This research will highlight a major impact of global warming on an important marine food web and will also inform conservation policy during this time of rapid ocean warming and changing copepod distribution.

In addition to disseminating our results "Open Access" in high-impact peer-reviewed scientific journals, and at national and international specialists conferences, we aim to conduct the following actions:1. Workshop on the conservation of sub-Antarctic seabirds in the context of the restructuring of food-webs. Representatives from RSPB, BirdLife International, JNCC, BAS, WWF, New Zealand Department of Conservation, UK Foreign & Commonwealth Office, will be and interested academics will be invited to participate in a Workshop on the implications of restructuring of sub-Antarctic pelagic foodwebs for the conservation of sub-Antarctic seabirds2. Publication of outreach booklet. We will prepare a briefing booklet suitable for nonspecialists, outlining the results from this research, and their implications in terms of understanding impacts of climate change on marine ecosystems.3. End of project demonstration event. This workshop will provide an opportunity to showcase the achievements of the project and to engage a broad range of stakeholders. Invitees will include representatives of global and UK statutory and NGO conservation bodies, managers (from Foreign & Commonwealth Office with responsibility for subAntactic islands and marine resources), and politicians with particular interest in climate change impacts and marine resources. Wider stakeholder interestThe general public are intensely interested in birds; the RSPB has over 1 million members. The public put huge quantities of food out in feeders and on birdtables to support their local birds. The public are also concerned about climate change effects, but have been confused by the many conflicting views expressed about climate change and predictions of future change scenarios. This project offers the opportunity to show clearly a change that is already occurring and how that change relates to food-web changes in a remote region of the globe. This will undoubtedly be of wide interest to the general public.Disseminating information to wider stakeholdersWe shall not only prepare press releases (through the University of Glasgow Press Office) to coincide with the scientific outputs from this research (papers in scientific journals, conference presentations and project workshops) but will also prepare specific non-specialist outputs for relevant public interest magazines such as the RSPB's Birds magazine, BBC Wildlife magazine. We will prepare posters suitable for display at the Scottish Seabird Centre (North Berwick) and at bird fairs and bird club conferences such as the British Trust for Ornithology conference and the Scottish Ornithologists Club conference. We will give talks on this research to bird clubs, conservation bodies and student societies and seminar groups.