Guest blog from Deborah Pardo, Richard Phillips and Phil Trathan, British Antarctic Survey

In Polar Regions, where species are already at the limit of their ranges, climate change is suspected to have particularly strong effects (Barbraud et al. 2012). Researchers at the British Antarctic Survey have been monitoring several key seabird colonies for a number of decades, as well as using animal-borne devices to better understand the links between population demography, and at-sea behaviour and distribution. Analyses of some of these monitoring data in relation to oceanographic and climatic variables provide a fantastic opportunity to understand the effects of climate change on Southern Ocean seabirds. 

Three of the 14 Overseas Territories (OTs) of the United-Kingdom are in the South Atlantic. These islands include the breeding sites of an array of Antarctic and sub-Antarctic species including albatrosses, penguins, petrels and skuas. Many of those species are currently listed as threatened by IUCN, and some of the populations in the UK OTs are at risk of extinction.

Recently, links have been made between changes in wind regimes in the Indian Ocean, and body size, breeding success and even survival probabilities of wandering albatrosses in the Indian Ocean (Weimerskirch et al. 2012). Stronger, more southerly winds appear to increase the ability of adults to move and access unpredictable resources. A shift in distribution might also reduce overlap with certain fisheries, reducing the risk of incidental mortality on longlines set for tuna and other billfishes.

A black browed albatross, one of the numerous species threatened with climate change in Southern Atlantic Ocean UK Overseas Territories

The effect of global warming is clearly evident at the Antarctic Peninsula where there are igher sea surface temperatures and reductions in seasonal sea ice extent. These physical changes may have profound effects on a range of trophic levels, in particular on the production of krill, which is at the base of trophic chains that sustain many marine bird and mammal populations in the Southern Ocean (Atkinson et al. 2004, Forcada et al. 2008-2009-2014, Reid and Croxall 2001). These changes may lead to range contractions, food-web perturbation and a poleward shift in distribution, as well as more variable breeding success and reduced population size. However the effect of such changes depends on the species, reflecting their specific life-histories and ecology. The case of penguins is particularly interesting; generalist gentoo penguins are seen as climate change ‘winners’, whereas Adélie and chinstrap penguins have become climate change ‘losers’ (Croxall et al. 2002, Boersma 2008, Trathan et al. 2014). Phenological changes have also been demonstrated, in particular in East Antarctica where 9 species of seabirds are breeding later, probably because changes in sea ice extent and duration have limited the quantity and availability of food prior to the breeding season (Barbraud & Weimerskirch 2006).

Given the complexity of processes underlying responses of seabirds to climate change, and the interaction with other environmental and anthropogenic drivers, a lot of unanswered questions still remain. Long-term monitoring of populations, the development of analytical tools and devices, and a strong collaboration between researchers to synthesize intra- and inter-specific responses in different regions will be keys to a better understanding of the effects of climate on Southern Ocean seabirds and our ability to predict their future.