This discussion was first published as part of the 2013 Red List update, but remains open for comment to enable reassessment in 2015.
White-chinned Petrel Procellaria aequinoctialis is currently classified as Vulnerable under criterion A4bcde, as it is suspected to be undergoing a decline of 30-49% over three generations (74 years).
South Georgia (Georgias del Sur) holds an estimated 773,000 pairs (ACAP 2009), 64% of the global population of 1,200,000 pairs. Kerguelen Islands (French Southern Territories) held a further 186,000-297,000 pairs in 2005 (Barbraud et al. 2009), or 16-25% of the global total. The Auckland Islands (New Zealand) hold the next largest population, 100,000 pairs in 1988 (ACAP 2009).
Globally, population data and trends are still lacking or are uncertain for a number of colonies. However, burrow occupancy declined by 28% on Bird Island, South Georgia (Georgias del Sur) during 1981–1998 (Berrow et al. 2000). Declines of 86% were recorded at sea in Prydz Bay, Antarctica between 1981-1993 (Woehler 1996). Population monitoring at a study plot on Marion Island recorded a 34% decrease in the population between 1997 and 2000 (Nel et al. 2002). Data from the Crozet archipelago indicate a 37% decline in breeding pairs between 1983 and 2004, based on population models and field estimates from two surveys (Barbraud et al. in litt. 2008). Data from at-sea surveys suggest a 35% decline in the Southern Indian Ocean during 1981-2007 (Péron et al. 2010a). On Iles Kerguelen, available population count data do not show any trend: 100,000-300,000 pairs in 1987 (Weimerskirch et al., 1989) compared with 186,000-297,000 in 2005 (Barbraud et al. 2009), however Barbraud et al (2009) concluded that the population may be in decline, based on data from fisheries and a population model.
No population trend estimates are available from the Auckland, Campbell, Antipodes or Prince Edward Islands, together representing approximately 17% of the global population.
However, even if colonies on Auckland, Campbell, Antipodes, Prince Edward and Kerguelen are assumed to be stable, based on an ongoing -1.6% decline per year on South Georgia (ACAP 2012) and declines in the smaller population on Crozet, the overall global population is projected to decline by 52% over three generations from 1980 (see attached spreadsheet). Martin et al. (2009) estimate a higher decline rate for South Georgia (-1.9% per annum), and if the population on Kerguelen was suspected to be declining then the rate of overall population decline could be higher. This suggests that despite considerable uncertainty over the trend data, an uplisting from Vulnerable to Endangered may be warranted.
Comments are invited on the population and trend estimates for this species and their implications for its potential uplisting, as well as the likely timing of when the trend may have exceeded 50% over three generations.
ACAP 2009. ACAP Species Assessment: White-chinned Petrel Procellaria aequinoctialis. Downloaded from http://www.acap.aq on 22 March 2013.
Barbraud, C.; Delord, K.; Marteau, C.; Weimerskirch, H. 2009. Estimates of population size of White-chinned Petrels and Grey Petrels at Kerguelen Islands and sensitivity to fisheries. Animal Conservation 12(3): 258-265
Berrow, S. D.; Croxall, J. P.; Grant, S. D. 2000. Status of White-chinned Petrels Procellaria aequinoctialis Linnaeus 1758, at Bird Island, South Georgia. Antarctic Science 12: 399-405
Martin, A. R.; Poncet, S.; Barbraud, C.; Foster, E.; Fretwell, P.; Rothery, R. 2009. The White-chinned Petrel (Procellaria aequinoctialis) on South Georgia: population size, distribution and global significance. Polar Biology 32: 655-661.
Nel, D.C., Ryan, P.G., Crawford, R.J.M., Cooper, J., and Huyser, O.A.W. 2002. Population trends of albatrosses and petrels at sub-Antarctic Marion Island. Polar Biology 25: 81-89
Péron, C.; Authier, M.; Barbraud, C.; Delord, K.; Besson, D.; Weimerskirch, H. 2010. Interdecadal changes in at-sea distribution and abundance of subantarctic seabirds along a latitudinal gradient in the Southern Indian Ocean. Global Change Biology 16: 1895-1909
Weimerskirch, H.; Zotier, R.; Jouventin, P. 1989. The avifauna of the Kerguelen Islands. Emu 89: 15-29
Woehler, E. J. 1996. Concurrent decreases in five species of Southern Ocean seabirds in Prydz Bay. Polar Biology 16: 379-382