Trends in the Breeding Population of Adélie Penguins in the , 1981-2012 Grant Ballard [email protected]

The abundance of breeding of aerial photographs of whales, another silverfish seabirds in a region is limited penguin colonies to consumer, were in recovery by food and nesting space determine annual population after the international availability. Adélie penguins sizes of penguin colonies in whaling moratorium went require both ice-free terrain the Ross Sea from 1981- into effect in 1982. for nesting and open ocean 2012. We found that the to find their food. Most of Adélie population in the Main Points does not meet Southern Ross Sea Numbers of Adélie penguins in one or both of these decreased from 1981 to the southern Ross Sea reached requirements. 2000, and then grew rapidly their highest recorded levels from 2009-2012, after shrinking from 2001 to 2012. from 1981-2000. Because of these constraints, population responses of An earlier study found that Climate factors and the Adélie penguins to changing Adélies decline after years of recovery of whale populations conditions can be complex. extensive winter sea ice in likely influenced the declining trend until 2000. Long-term climate change the Ross Sea – conditions and shorter-term presumably unfavorable for Depletion of , atmospheric variability can inexperienced penguins a competitor with penguins for have major impacts to trying to survive their first smaller fish, may explain the sharp increasing trend in recent nesting, foraging, and winter. But recent years have years. migratory conditions. seen the highest extents of winter sea ice ever recorded. Lyver PO, Barron M, Barton KJ, Significant changes in Adélie Ainley DG, Pollard A, Gordon S., penguin and other Antarctic We propose that unfavorable McNeill S., Ballard G, Wilson P.R. 2014. Trends in the Breeding marine predator populations winter ice conditions have Population of Adélie Penguins in have also been linked to been offset by the Antarctic the Ross Sea, 1981–2012: A Coincidence of Climate and depletion of whales and toothfish fishery (which Resource Extraction Effects. PLoS large fish, which compete for began in 1997) by reducing ONE 9(3): e91188. limited numbers of prey competition for one of the doi:10.1371/journal.pone.0091188 . penguins’ main prey species: Antarctic silverfish. The To begin to assess the earlier decline in penguin relative roles of these factors, populations coincides with a we used a long-term series period when Antarctic minke

Sep. 22, 2014, Point Blue Conservation Science visit www.pointblue.org/publication-briefs