Macaroni Penguin (Eudyptes chrysolophus): correctly listed as Vulnerable?

September 5, 2011 by Joe Taylor

 

 

BirdLife species factsheet for Macaroni Penguin
Macaroni Penguin Eudyptes chrysolophus breeds in at least 216 colonies at 50 sites in the higher latitudes of the southern hemisphere (Woehler 1993, Woehler and Croxall 1999). The total population is estimated by BirdLife to be c.9 million pairs, although it is argued that this is likely to be an underestimate because of potential underestimates in the South Georgia Island region (USFWS 2008). The species is listed as Vulnerable under criteria A2b,c; A3b,c; A4b,c, on the basis that the global population appears to have declined rapidly, by 30-49% over the preceding three generations, estimated to be c.34 years, and it is projected to decline by 30-49% over the next three generations. As noted in the assessment, however, the current classification is heavily reliant on the extrapolation of small-scale data, thus large-scale surveys are needed to confirm this categorisation.

The current trend estimate is based on recorded local declines. Populations on South Georgia and Bouvet Islands probably increased substantially in the 1960s and 1970s, but have subsequently decreased. Study populations on South Georgia declined by 65% from 1986 to 1998 (J. P. Croxall unpublished data), and the overall South Georgia population probably halved between c.1978 and 1998 (Trathan et al. 1998). Study populations on Marion Island decreased by 50% between 1979 and 1998. In contrast, populations on Kerguelen increased by c.1% per year between 1962 and 1985, and subsequent data from 1998 indicated that the colonies were stable or increasing (H. Weimerskirch per T. Micol in litt. 1999). Populations in South America may be stable, but data are scant.

The validity of the current assessment for this species has been brought into question by a review by the US Fish and Wildlife Services (USFWS 2008). Criticism was levelled at the use of trends at small study colonies to estimate the overall trend for the Prince Edward Islands. Likewise, the conclusion that overall numbers on South Georgia declined by 50% in the last two decades of the 20th century was criticised because it has not been empirically verified in the literature. Although the species is thought to have undergone a recent decline on Bouvet Island, there are apparently no current estimates for the population there. Significant recorded declines in colonies on Marion Island have also been questioned due to changes in survey methodology, and an overall decline of 18% in the island’s estimated total population between 1994-1995 and 2002-2003 is not considered significant by the USFWS (2008) in the context of small fluctuations in the three subsequent three breeding seasons. It has also been asserted that the decline noted on Prince Edward Island between 1976-1977 and 2001-2002, in which the estimated population fell from c.17,000 pairs to c.9,000 pairs (Crawford et al. 2003) was overestimated, and that the overall decline on Marion and Prince Edward Islands combined (c.3.4% of the species’s global population) was 32% between 1979 and 2003 (USFWS 2008).

These criticisms, combined with suggestions that some populations are stable or increasing, or have unknown trends, suggest that the overall estimated rate of decline should be reduced for this species. Comments on the current listing and further information on the species are requested.

References:

Crawford, R. J. M., Cooper, J., Dyer, B. M., Greyling, M., Klages, N. T. W., Ryan, P. G., Petersen, S., Underhill, L. G., Upfold, L., Wilkinson, W., de Villiers, M., du Plessis, S., du Toit, M., Leshoro, T. M. et al. (2003) Populations of surface nesting seabirds at Marion Island, 1994/95-2002/03. Afr. J. Mar. Sci. 25: 427-440.
Trathan, P. N., Croxall, J. P., Murphy, E. J. and Everson, I. (1998) Use of at-sea distribution data to derive potential foraging ranges of macaroni penguins during the breeding season. Mar. Ecol. Prog. Ser. 169: 263-275.
USFWS (2008) Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List Four Penguin Species as Threatened or Endangered Under the Endangered Species Act and Proposed Rule To List the Southern Rockhopper Penguin in the Campbell Plateau Portion of Its Range. Federal Register, Vol. 73: No. 244.
Woehler, E. J. (1993) The distribution and abundance of Antarctic and Subantarctic penguins. Cambridge, U.K.: Scientific Commission on Antarctic Research.
Woehler, E. J. and Croxall, J. P. (1999) The status and trends of Antarctic and subantarctic seabirds. Mar. Ornithol. 25: 43-66.

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