Going down in the south: Southern Giant Petrels decreasing on Antarctic Signy Island

Mike Dunn and colleagues (British Antarctic Survey, Cambridge, UK) have published online in the journal Polar Biology on population changes of Southern Giant Petrels Macronectes giganteus breeding on Signy Island in the South Orkney Islands.  “A fifty year study of the charismatic seabird, the southern giant petrel, on the Antarctic island of Signy shows its population has halved and its breeding success has declined in the last 10-20 years.”

The paper’s abstract follows:

“The southern giant petrel (Macronectes giganteus) has a circumpolar distribution and breeds on subantarctic islands and a few continental Antarctic sites.  Although this species has recently been down-listed to “Least Concern” by the World Conservation Union (IUCN), there are strong fluctuations in abundance and variable long-term trends recorded at different sites.  Systematic, long-term monitoring is essential to determine drivers underlying its population dynamics.  Here, we examine long-term changes in population size and productivity of southern giant petrels at Signy Island, South Orkney Islands.  Comparing estimated numbers of breeding pairs over the whole island in 2000/2001, 2005/2006, 2009/2010 and 2014/2015 with historical data revealed several phases of population change: a 64 % decline (6.2 % per annum) from 1968/1969 to 1984/1985, a 162 % increase (6.2 % per annum) to 2000/2001, stability until 2005/2006, a 56 % decline (18.3 % per annum) to 2009/2010 and stability until 2014/2015. This represents a 1.8 % decline per annum between 1968/1969 and 2014/2015.  Annual counts within focal study areas suggested a more rapid increase from 1996/1997 to 2006/2007, but the same downward trend from 2006/2007 to present, underlining potential pitfalls in inferring trends from part-island counts.  There was also a 20 % decline in breeding success from 1996/1997 to 2014/2015.  Our results indicate substantial fluctuations in southern giant petrel abundance at Signy Island over 4–5 decades and a recent decline in breeding numbers and success.  As the southern giant petrels breeding at the South Orkney Islands represents [sic] ~5–10 % of the global population, continuation of these declines would be of high conservation concern.”

Read a press release on the publication.

Southern Giant Petrel on Signy Island, photograph by Mike Dunn

With thanks to Richard Phillips for information.

Reference:

Dunn, M.J., Jackson, J.A., Adlard, S. & Phillips, R.A. 2015.  Population size and trends of southern giant petrels (Macronectes giganteus) nesting at Signy Island, South Orkney Islands.  Polar Biology doi:10.1007/ s00300-015-1855-0.

John Cooper, ACAP Information Officer, 22 December 2015