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The Distribution, Abundance and Population Trends of Gentoo,
Rockhopper and King Penguins at the Falkland Islands

by Mike Bingham. Published 1998 in ORYX 32(3): 223-32.

SUMMARY

The Falkland Islands are a globally important breeding location for seabirds, including penguins. The total breeding populations of three of the four main penguin species present in the Falklands were censused in the austral summer of 1995/96. The results for gentoo and rockhopper penguins suggest declines of about 43% and 90% respectively since a similar census in 1932/33. Recent monitoring studies suggest that these declines are still continuing; research to investigate causes (likely to reflect changes in the marine, rather than terrestrial environment) is a high priority. In contrast king penguin populations, currently c.400 pairs, have increased steadily, by 700% since 1980/81, in line with world-wide trends for this species.

INTRODUCTION

The Falkland Islands lie in the South West Atlantic, approximately 450 km. north east of the southern tip of South America. The archipelago is made up of two main islands, and several hundred smaller islands, which are home to large numbers of breeding seabirds, including penguins. The Falkland Islands have the world's largest breeding population of rockhopper penguins (Eudyptes chrysocome chrysocome), and the second largest population of gentoo penguins (Pygoscelis papua) (Croxall et al. 1984).

Data gathered from breeding colonies around the Falklands during the past 10 years, suggested a decline in the breeding population of gentoo and rockhopper penguins (Bingham 1995). The only comprehensive island-wide population census for these species was in 1932/33; a repeat census was needed to confirm whether declines were occurring throughout the islands, and to estimate their magnitude. In addition, the census would establish comprehensive baseline data to complement current monitoring studies. The imminent exploration for oil in Falklands waters, makes the establishment of baseline data for these species particularly important, because of their potential high vulnerability to oil pollution.

The Falklands' population of king penguin (Aptenodytes patagonicus), is very small, but was still included in the census. The fourth main Falklands' penguin, the magellanic penguin (Spheniscus magellanicus), was not included in this census due to the difficulties of censusing a species that nests in burrows.

METHODS

Most breeding site locations were already known from fieldwork conducted prior to the 1995/96 census; however this information was checked by extensive consultation with landowners, to ensure that sites were not overlooked.

For a comprehensive census of such a large area, it was only possible to make a single visit to each site. Counts made during a single visit will inevitably underestimate the total number of breeding pairs, because of omitting pairs that have either not yet laid their eggs, or those that have already laid and subsequently failed. In general, counts were timed to correspond with the end of the egg-laying period, thereby ensuring that few pairs were still to lay, and allowing an assessment to be made of the underestimate due to pairs failing, by using failure rates during incubation from other studies.

The gentoo penguins concluded their first egg-laying by the end of October 1995. The 1995/96 census counted 15% of the gentoo population between 15 - 31 October, and the remainder between 1 November and 1 December. Because gentoos failing early tend to re-lay, and failure rates during incubation are low (c.1% per week), the magnitude of any underestimates resulting from differences in survey dates should be well below 5%.

Rockhopper penguins are much more synchronous, in terms of egg-laying, than gentoo penguins. Laying was concluded by mid-November 1995, and the 1995/96 census counted 98% of the rockhopper population between 1 November - 1 December (2% between 2-18 December). Repeated counts of rockhopper colonies in previous years showed that nest counts drop at a rate of about 3% per week for the first month after egg-laying, as a result of failed nests. It is therefore unlikely that the average underestimate of rockhopper populations exceeded 10%.

For most rockhopper and all gentoo breeding sites, the recorder made two separate counts of all occupied nests using a tally counter. The mean of the two counts was taken as the number of breeding pairs. Where these two counts differed by more than 10%, a third count was taken to give a mean value of three counts. In practice this was rarely necessary, and the spread of results was generally well below plus or minus 5%. Reference photographs were also taken at most sites for future comparison.

For the very large rockhopper colonies on Steeple Jason, Grand Jason, Bird and Beauchene Islands, direct ground counts were not possible. These sites were counted using a total of 60 randomly selected sample plots to determine the range of nesting densities, and the areas of the colonies was determined, to enable calculations of total breeding pairs to be made. A minimum of 10% and a maximum of 15% of the total colony area was sampled at each of the three sites. These measurements of area and density taken during the site visits were later compared against aerial photographs taken of the colonies. The margin of error for this methodology is greater than for direct counts, but should be within plus or minus 10%.

The breeding cycle of the king penguin is different from that of gentoos and rockhoppers, with chicks over-wintering at the colony, and a complete breeding cycle lasting over a year. This tends to result in individual birds having their following breeding cycle out of phase with its predecessor; thus large chicks and eggs may both occur in a colony at the same time. This complicates assessment of the breeding populations, and chick counts were taken instead. The estimation of error for chick counts is well below 5%, but will underestimate the number of breeding pairs by about 20% (Lewis Smith & Tallowin 1979).

RESULTS

KING PENGUIN

The 1995/96 census recorded a total of 339 chicks for the Falklands as a whole. Allowing for losses during incubation and chick-rearing, and the staggered breeding cycle, this figure gives an estimated Falklands population of around 400 breeding pairs. Volunteer Point, on the north-east coast of East Falkland, was the only king penguin breeding colony in the Falkland Islands, with individual pairs breeding in gentoos colonies at all other sites .

GENTOO PENGUIN

The 1995/96 population of gentoo penguins in the Falkland Islands was about 65,000 breeding pairs, with an estimated range of 61,750 - 68,250 pairs. There was a total of 81 breeding sites distributed throughout the archipelago, ranging in size from 7 to 5100 breeding pairs. Eighteen sites had breeding populations of >1000 pairs, between them totalling 58% of the overall population. The general distribution was: East Falkland - 16,000 pairs (24.5%), West Falkland - 24,000 pairs (37%) and Outer Islands - 25,000 pairs (38.5%).

ROCKHOPPER PENGUIN

The 1995/96 population estimate for rockhopper penguins in the Falkland Islands was 297,000 breeding pairs, with an estimated range of 267,000 - 327,000 pairs. There was a total of 36 breeding sites, ranging in size from 83 to 115,000 breeding pairs. These sites are distributed around most of the Falklands, but the greatest concentrations are on the outer islands. The general distribution was: East Falkland - 21,000 pairs (7%), West Falkland -11,000 pairs (4%) and Outer Islands - 265,000 pairs (89%).

DISCUSSION

KING PENGUIN

The present Falklands` population of around 400 breeding pairs is almost entirely concentrated at one location on the north-east of East Falkland. This colony has expanded from 38 chicks in 1980/81 (N. Keenleyside, unpublished data) to 330 chicks in 1995/96. Nevertheless this comprises less than 0.1% of a world population that has been increasing consistently since the 1970's (Woehler 1993), and the high rate of increase in the Falklands during this period is likely to be due in part to immigration from the large and expanding population on South Georgia. At least one bird banded on South Georgia has been resighted in the Falklands (O. Olsen, pers comm).

GENTOO PENGUIN

The Falkland Islands are one of twelve major breeding sites for this species (Robertson 1986). The 65,000 pairs in the Falklands are widely distributed throughout the archipelago, and represent about 20% of the world population; second in size only to South Georgia. Within the Falklands there are three sites (New Island, Steeple Jason and Saunders Island) that each hold more than 1% of the estimated world population of 318,000 pairs. However, comparison with Bennett's (1933) total of 116,000 pairs for the Falklands during 1932/33 suggests an overall decline of around 45%.

Comparison of single years, widely separated in time, can sometimes be unreliable, especially in a species whose population shows considerable interannual fluctuation (Croxall & Rothery, 1995). However, population counts from 21 colonies which have been monitored since 1988/89 show that the 1995/96 census did not coincide with a season of especially low population. Moreover, these data suggest that the decline has been continuing in recent years. Although no records exist as to the methodology employed during Bennett's (1933) census, his numerous publications testify to his reputation as a meticulous and experienced observer and naturalist, and gentoo penguins are a particularly easy species to count accurately. Even if the larger and hence more difficult sites such as the Jason Islands are excluded, comparable counts for the remaining sites still indicate a decline over the 60 year period.

ROCKHOPPER PENGUIN

The Falklands population, of around 300,000 pairs, represents the world's most important breeding site for this species. In addition, the Falkland Islands have 63% of the world population for this sub-species, with most of the remainder being on islands around the coast of Chile (Bingham and Mejias, In press). In the Falklands, the islands of Steeple Jason and Grand Jason to the north-west, and Beauchene to the south, hold the only very large concentrations (> 20,000 pairs) and these account for around 75% of the Falklands population.

Population counts from study sites monitored throughout the 1990's show that the 1995/96 census did not coincide with a year of naturally low populations. Thus the current population estimate is very considerably lower than the 3,169,000 pairs recorded by Bennett (1933) in 1932/33. Although Bennett gave no account of the methodology used, he states that his figures were most likely to be underestimates, and did not include the large colonies on Beauchene and Bird Island which currently hold 28% of the Falklands population. It therefore appears that the Falklands population has declined to about 10% of its 1932/33 level.

POPULATION CHANGES

Whereas populations of king penguins in the Falklands have increased in recent years, in line with world-wide trends, populations of gentoo and rockhopper penguins have decreased substantially over the last 60 years, perhaps by as much as 50% and 90% respectively. This is supported by data from more recent site studies which also suggest that the declines have continued into recent years. Kidney Island's rockhopper population declined from 3,000 pairs in 1960/61 to 240 pairs in 1994/95 (Bingham 1995), rockhopper colonies at New Island declined from >100,000 pairs in 1976/78 to 4,000 pairs in 1992 (Thompson 1993), and at Beauchêne Island the colony had declined from 300,000 pairs in 1980 (Lewis-Smith and Prince 1985) to 71,500 pairs in 1991 (Thompson 1993). The 1985/86 summer season was especially bad for rockhoppers, with tens of thousands of adults dying from starvation during their annual moult. Analysis of carcasses showed that they had died from starvation, and this was likely to have resulted from food shortages prior to the moult (Keymer, 1988).

It is not easy to account for these declines. Direct exploitation of penguins has diminished to insignificance. Killing birds to extract oil ceased at the beginning of the 20th century, and collecting of eggs for food has now declined to very low levels.

Commercial fisheries started around the Falklands in the 1960's, expanded greatly during the 1970's and 1980's, and in recent years has been generally stable since the Falkland Islands Government imposed a licensing regime in 1985. There is some evidence that penguin population size and breeding performance is related to food availability around the Falklands (Keymer, 1988; Thompson, 1989,1993; Bingham, 1995). There is no direct evidence that food availability to penguins has been affected by commercial fishing, but this possibility cannot be ruled out, especially in respect of squid fisheries, larval/juvenile squid being an important element of the diet of both rockhopper and gentoo penguins (Thompson 1994). It should also be noted that the breeding season diet of rockhoppers, appears to comprise of more Euphausids and less commercially fished species than that of the gentoo (Thompson 1993).

Loss or degradation of breeding habitat has probably occurred at some sites. due to erosion, fire or other anthropogenic activity. Disturbance from humans and stock may also have been (and remains) a problem in some areas, though there is little firm evidence that this or the current level of tourist visits have any discernible influence. Overall, none of these effects can explain large scale changes, especially at sites where breeding habitat loss and disturbance have been minimal or non-existent. There is also no evidence of increased impact from introduced predators, and many sites lack any introduced predatory species.

Rockhopper Penguins (of the subspecies E.c. filholi) have declined very substantially at the New Zealand Sub-Antarctic islands since the 1940's (Cunningham & Moors 1994, Cooper 1992). At these sites also there was no evidence that land-based influences were responsible. It was therefore suggested that changes in the marine environment may have occurred and affected the survival of penguins, either directly through physical factors or, more likely, indirectly through changes to the food web.

At a recent international workshop reviewing the status of penguins, it was clear that the large-scale declines in rockhopper penguin populations were of such magnitude as to justify treating the species as globally threatened (Vulnerable), according to the new IUCN criteria. A co-ordinated programme of research on this species at its most important population site, the Falkland Islands, is now long overdue.

ACKNOWLEDGEMENTS

My thanks go to the RAF Ornithological Society, and other dedicated volunteers who assisted with the surveys, the Commander, British Forces Falkland Islands, for arranging logistical support and aerial photographs, the Wellcome Trust for funding the project, and Dr. John Croxall for assisting with drafting the manuscript. Thanks to all the landowners who, virtually without exception, offered support in providing information, assistance and access to their land.

REFERENCES

Bennett, A.G. 1933. The penguin population of the Falkland Islands in 1932/33. Government Press, Falkland Islands. 4pp.

Bingham, M. 1995. Population status of penguin species in the Falkland Islands. Penguin Conservation, 8.1, 14-19.

Bingham, M. and Mejias, E. In Press. Penguin populations of the Magellanic Region. Scientia Marina.

Cooper, W. 1992. Rockhopper Penguins at the Auckland Islands. Notornis, 39, 66-67.

Croxall, J.P. 1992 Southern ocean environmental change: effects on seabird, seal and whale populations. Philosophical Transactions of the Royal Society of London, B, 338, 319-328.

Croxall, J.P. and Rothery, P. 1995. Population change in Gentoo Penguins Pygoscelis papua at South Georgia: potential roles of adult survival, recruitment and deferred breeding. In Penguin biology: Advances in research and management (eds P. Dann, I. Norman and P. Reilly) pp. 26-38. Surrey Beatty & Sons, Chipping Norton, Australia.

Croxall, J.P., McInnes, S.J. and Prince P.A. 1984 The status and conservation of seabirds at the Falkland Islands. In Status and conservation of the world's seabirds. ICBP Technical Publication No.2. 271-291.

Cunningham, D.M. and Moors, P.J. 1994. The decline of Rockhopper Penguins Eudyptes chrysocome at Campbell Island, Southern Ocean and the influence of rising sea temperatures. Emu, 94, 27-36.

Fraser, W.R., Trivelpiece, W.Z., Ainley, D.G. and Trivelpiece, S.G. 1992. Increases in Antarctic penguin populations: reduced competition with whales or a loss of sea ice due to environmental warming? Polar Biology, 11, 525-531.

Keymer, I.F. 1988. An investigation of Rockhopper Penguin mortality in the Falklands during the 1985/86 breeding season. Falkland Islands Foundation Project Report, Falkland Islands. 19pp.

Lewis Smith, R.I. and Tallowin, J.R.B. 1979. The distribution and size of King Penguin rookeries on South Georgia. British Antarctic Survey Bulletin, 49, 259-76.

Lewis Smith, R.I., & Prince, P.A. 1985. The natural history of Beauchene Island, Falkland Islands. Biological Journal of the Linnean Society, 24, 233-283.

Robertson, G. 1986. Population size and breeding success of the Gentoo Penguin at Macquarie Island. Australian Wildlife Research, 13, 583-587.

Thompson, K.R. 1989. An assessment of the potential for competition between seabirds and fisheries in the Falkland Islands. Falkland Islands Foundation Project Report, Falkland Islands. 94pp.

Thompson, K.R. 1993. Falkland Islands Seabird Monitoring Programme Summary of Results. Falklands Conservation Report SMP/3, Falkland Islands. 25pp.

Thompson, K.R. 1994. Predation on Gonatus antarcticus by Falkland Islands seabirds. Antarctic Science, 6, 269-274.

Woehler, E.J. 1993 The Distribution and Abundance of Antarctic and Subantarctic Penguins. Scientific Committee on Antarctic Research, University Printing Services, Cambridge. 76pp.

Other Research Publications

1) Bingham, M. (2002) The decline of Falkland Islands penguins in the presence of a commercial fishing industry.

2) Bingham, M. (1998) The distribution, abundance and population trends of Gentoo, Rockhopper and King penguins at the Falkland Islands. Orxy 32(3): 223-32.

3) Bingham, M. (1996) Censo de los pingüinos de las Islas Falklands. Unpublished Spanish resume of above.

 

4) Bingham, M. (1998) Penguins of South America and the Falkland Islands. Penguin Conservation 11(1): 8-15.

5) Bingham M. and Mejias E. (1999) Penguins of the Magellan Region. Scientia Marina Vol:63, Supl. 1: 485-493

6) Bingham, M. (1999) Field Guide to Birds of the Falkland Islands.

7. Bingham, M and Herrmann, T (2008) Magellanic Penguin Monitoring Results for Magdalena Island 2000-08. Anales Instituto Patagonia (Chile) 36(2): 19-32.

 

 
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