Penguins of the Magellan region *

During 1995/96, a population census of all penguin species (except the Magellanic Penguin) was conducted around the Falkland Islands (Bingham, 1998b). Every breeding colony was visited, and population totals for each species obtained. Comparing these data with previous studies revealed that the Southern Rockhopper population had crashed to a fraction of its former size (Bennett, 1933; Bingham 1994c, 1995a, 1998b). With no obvious reason for this dramatic decline, apart from speculation about commercial fishing, it became a priority to census the remainder of the world population located in South America, to determine how wide-spread the decline had been. It had been shown during the 1995/96 census of the Falkland Islands, that it requires little extra effort to census all penguin species during the course of such a census. The only exception to this was the Magellanic Penguin, which because of its widespread, low-density distribution in burrows, made it SCI. MAR., 63 (Supl. 1): 485-493 SCIENTIA MARINA 1999

impossible to census with methods employed for surface nesting species (Bingham, 1998b).For this reason the Magellanic Penguin had been excluded from the Falkland Islands census.On that basis it was decided that a census would be conducted of all South American penguins during the 1996/97 breeding season, except for those of the Genus Spheniscus.
During the 1995/96 Falkland Islands census it had been possible to conduct ground counts of incubating pairs at each of the breeding colonies, because most colonies were relatively accessible (Bingham, 1998b).By contrast, many of the South American colonies are remote and inaccessible, and any attempt to conduct ground counts of each and every colony would have been doomed to failure.It was therefore decided from the outset that the census would be conducted by light aircraft, thereby negating the need to get ashore at difficult and remote sites.
The location of all the Falkland Islands breeding sites had been known prior to the commencement of the 1995/96 census (Bingham, 1998b), but this was certainly not the case for South America.Although data did exist for a number of known breeding sites around South America (Frere et al., 1993;Venegas 1984Venegas , 1991;;Woehler, 1993), it was likely that other sites existed which had not been recorded.This was another reason for favouring an aerial census, since it provided the opportunity to cover large areas of suitable coastline in search of previously unrecorded colonies.This reduced the margin of error that would otherwise arise from new sites being overlooked, however the margin of error for aerial counts was likely to be higher than for ground counts.
In order to quantify the margin of error likely to be expected from aerial counts, a number of aerial censuses were made of Rockhopper colonies in the Falkland Islands for which the number of breeding pairs was also determined by ground counts.These aerial counts differed by a maximum of 14% from ground counts made of the same colony, suggesting a total margin of error of ± 20% for aerial census data (Bingham 1998a,b).
The 1996/97 aerial census was conducted throughout the known Eudyptes breeding ranges of Chile and Tierra del Fuego (Woehler, 1993).The Atlantic coast of mainland Argentina was excluded from the census, since this coastline has been well studied, and does not hold any breeding sites for species covered by the census, other than a very small Rockhopper colony on Isla Pingüino, near Puerto Deseado (47º45'S 65º54'W) (Frere et al., 1993, Gandini et al., in press).This colony is regularly monitored as part of an ongoing research programme, and population data from that research was used in favour of duplicating results (Frere et al., 1993).

King Penguin
King Penguins do not make nests, but instead hold eggs and chicks on their feet, making nest counts impossible.For this reason counts are made of chicks and a conversion factor used (Lewis Smith and Tallowin, 1979).The Falkland Islands population census recorded 339 chicks, which equals a total breeding population of approximately 400 breeding pairs (Bingham, 1998b) (Figure 1;Table 1).
King Penguins have not bred in South America since the colony on Islas de los Estados (54º50'S 64º00'W) was wiped out by sealers during the last century (Prosser Goodall, 1979).No King Penguins were recorded anywhere in South America during 1996/97.

Gentoo Penguin
The Falkland Islands hold around 20% of the world population of Gentoo Penguin, with a total population of 65,000 breeding pairs at 81 sites being PENGUINS OF THE MAGELLAN REGION 487 recorded during 1995/96 (Bingham, 1998b) (Figure 2; Table 2).Somewhat surprisingly, a very small Gentoo breeding colony was discovered on Islas de los Estados (54º50'S 64º00'W), containing almost 100 breeding pairs.This was the only breeding colony of Gentoo Penguin recorded in South America.

Southern Rockhopper
The Falkland Islands and South America are home to two species of the genus Eudyptes; the Southern Rockhopper and the Macaroni (Bingham, 1998a) that is restricted to the Falkland Islands and South America (Bingham, 1998b).
The 1996/97 census showed that South America holds a breeding population of about 175,000 pairs of Southern Rockhoppers, at a total of 15 breeding sites (Figure 3; Table 3).Apart from the very small colony on Isla Pingüino (Frere et al., 1993), these breeding sites are restricted to the islands off Tierra del Fuego and Chile.Combined with the Falkland Islands census total of 300,000 pairs at 36 sites (Bingham, 1998b) (Figure 4; Table 4), this gives a world population of 475,000 breeding pairs at 51 sites for the subspecies Eudyptes c. chrysocome.(South Georgia has been known to hold a few breeding pairs, but no more than 10 pairs have been recorded).

Macaroni Penguin
The Falkland Islands population of Macaroni Penguins is very small, with no individual colonies and only individual pairs found breeding amongst PENGUINS OF THE MAGELLAN REGION 489 Rockhoppers colonies.The total Falklands population stands at less than 50 pairs (Bingham,1998a).
The 1996/97 census showed that South America holds a breeding population of about 12,000 pairs of Macaroni, at a total of nine sites (Figure 5; Table 5).These sites are all restricted to the islands off Tierra del Fuego and Chile.Only the islands of Diego Ramirez, Ildefonso and Noir hold more than a thousand breeding pairs.

Magellanic Penguin
Of the five species of penguin that regularly breed within the Magellan region, the Magellanic Penguin is the most numerous and widespread (Bingham, 1998a).It only breeds around the coasts of Chile and Argentina, and at the Falkland Islands.

DISCUSSION
The Falkland Islands population of around 400 breeding pairs of King Penguin has rapidly expand-490 M. BINGHAM and E. MEJIAS  ed from a population of less than 100 pairs recorded during 1980/81 (Bingham, 1995a).With a world population of around 1,500,000 pairs (Woehler, 1993), the Falkland Islands population is of regional rather than global importance.
Annual counts of selected breeding sites around the Falkland Islands suggested that much of this decline had occurred during the late 1980s and early 1990s, with low breeding success also being observed during that period (Bingham, 1994a(Bingham, , d, 1995a)).Continued monitoring of these sites since the census indicates that by 1997/98 the Falkland Islands population had risen to around 81,000 breeding pairs (Fig. 6), with high breeding success rates having been recorded from 1993/94 through to 1997/98 (Fig. 7).Gentoo populations are known to fluctuate greatly, and it is plausible that the decline observed previously was merely part of a natural cycle.
The world population of Southern Rockhopper Penguin now stands at around 475,000 breeding pairs, with 63% of the population in the Falkland Islands and 37% in South America.Comparison with previous census data (Bennett, 1933) indicates that the Falkland Islands population has crashed to just 10% of its former size, with much of this decline having occurred during the 1980s and early 1990s (Bingham, 1994c(Bingham, , 1995a(Bingham, , 1998b)).Evidence of this dramatic decline can also be seen from the breeding sites themselves.The Falkland Islands breeding sites feature old colonies which have destroyed the vegetation by years of occupancy, leaving only lichen covered rocks and stones around the nest-site.The huge breeding colonies that once produced these areas of barren ground, have now been reduced to small clusters of birds huddled in the centre of their stony territories.
The South American population shows no such evidence of decline, with breeding sites featuring a healthy mixture of new, middle-aged and old colonies, indicating a natural cycle of fluctuation and regeneration.Comparison with previous census data (Venegas, 1984(Venegas, , 1991;;Woehler, 1993) also indicates that the South American population was stable throughout the 1980s and 1990s, during which the Falkland Islands population crashed (Bingham 1998b).The reason for such differing fortunes is unknown, although it is interesting to note that the waters around Tierra del Fuego and Chile are not heavily fished, whilst those around the Falkland Islands are (Falkland Islands Government, 1989).In the Falkland Islands, even internationally recognised sites, such as Beauchêne Island which is being considered for World Heritage status, have fleets of fishing boats operating just 3 miles from breeding Rockhoppers.
The Macaroni Penguin populations of South America (12,000 pairs) and the Falkland Islands (<50 pairs) must be looked at in the light of a world population of around 9 million breeding pairs (Bingham, 1998a;Woehler, 1993).These populations are therefore of regional rather than international importance.There were no obvious signs of decline amongst the South American population, and no evidence to suggest that the population has changed greatly over recent years.The Macaroni is the most numerous of all the world's penguins.Although Magellanic Penguins were not included in the 1995/96 and 1996/97 censuses, that is not to say that no work has been done on this species.The current population along the coast of mainland Argentina is estimated to be 650,000 breeding pairs (Gandini et al., in press).Observations of distribution around Tierra del Fuego and Chile during the 1996/97 census suggest that these regions hold a population at least as large as that of mainland Argentina, giving a South American population of at least 1,300,000 pairs.The Falkland Islands population is well in excess of 100,000 pairs (Bingham, 1998a), giving a minimum world population of around one and a half million breeding pairs (Fig. 8).
Annual monitoring of selected colonies (Bingham, 1994b(Bingham, , 1995a, b) , b) shows that the Magellanic Penguin population of the Falkland Islands has declined to about half its 1980s level (Fig. 9).These declines coincided with observations of low breeding success up until 1993/94 (Fig. 10).
In addition to its Penguin Monitoring Programme in the Falkland Islands, the Environmental Research Unit now conducts similar studies at a number of Chilean breeding sites along the Straits of Magellan.These studies suggest that the Magellanic Penguin decline observed in the Falkland Islands has not been evident in the Magellan region of Chile, despite its close proximity and similar breeding habitat to the Falkland Islands (Bingham, 1998a).
Further evidence of the differing fortunes of the two regions can be seen from the breeding sites themselves.Magellanic Penguin colonies around the Falkland Islands generally feature a very high percentage (on average more than 70%) of unoccupied burrows.Similar breeding sites in the Straits of Magellan hold less than half the proportion of unoccupied burrows (< 35%), suggesting lower levels of adult mortality or higher levels of recruitment (Bingham, 1998a).There is no large-scale fishery in the Straits of Magellan.