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SCAR Bulletin 150, July 2003

Management Plan for
Antarctic Specially Protected Area No. 117
Avian Island, Marguerite Bay, Antarctic Peninsula

ASPA 107 ASPA 108 ASPA 117 ASPA 121 ASPA 123 ASPA 124 ASPA 126

ASPA 117 Annex 1

CLIMATE AND SEA ICE GEOLOGY, GEOMORPHOLOGY AND SOILS TERRESTRIAL BIOLOGY STREAMS AND LAKES
BREEDING BIRDS BREEDING MAMMALS AND THE MARINE ENVIRONMENT HUMAN ACTIVITIES / IMPACTS

6(i) Additional information on the natural features of the Area.
CLIMATE AND SEA ICE
No extended meteorological records are available for Avian Island, but records from 1962-74 for Adelaide Base (formerly UK; now Teniente Luis Carvajal, Chile), 1.2 km distant, show a mean daily maximum temperature of 3ºC in February (extreme maximum 9ºC) and a mean daily minimum of -8ºC in August (extreme minimum -44ºC). The same general pattern was observed in year-round observations made on the island in 1978-79 (Poncet and Poncet 1979). Precipitation on the island in this year was usually as snow, most of which fell between August and October, but with occasional snowfalls and some rain in the summer.
Marguerite Bay usually freezes in winter, although the extent and character of sea ice shows considerable inter-seasonal variation. Occasionally Marguerite Bay may not clear of ice completely until February or March, at which time the sea may again begin to freeze. Despite the extent and frequent persistence of regional sea ice, a recurrent polynya has been observed near Avian Island, which can provide locally ice-free conditions from October onward. In addition, strong tidal currents around Avian Island help to keep surrounding waters ice-free for much of the year, which facilitates easy access to feeding grounds for several species. The island is not particularly windy, with an annual average of 10 knots in 1978-79. However, the strong katabatic winds that descend from Adelaide Island, perhaps for 1-3 days a few times every month, reduce snow accumulation on the island and push sea ice away from the coast, helping to form the polynya. The relatively snow-free conditions are important for bird colonisation.

GEOLOGY, GEOMORPHOLOGY AND SOILS
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The bedrock of Avian Island forms the eastern limb of a NNE – SSW trending synclinal structure at the southwestern end of Adelaide Island and is composed of interbedded lithic-rich and feldspar-rich volcaniclastic sandstones. Bedded tuffaceaous sandstones, pebbly sandstones rich in volcanic lithics, and a volcanic granule breccia also occur. The latter is probably a primary volcanic deposit, while the rest of the sequence is largely composed of reworked volcanic material. The sequence forms part of the Antarctic Peninsula Volcanic Group and is of Jurassic to early Tertiary age (Griffiths 1992, Moyes et al 1994). Apart from rock outcrop, the surface consists mainly of frost-shattered rock with permafrost. Ornithogenic soils are widespread, particularly in the north; organic peat soil is virtually absent, but where present is not well-developed and is associated with moss growth. Several raised beaches have been noted on Avian Island, but the geomorphology has not otherwise been described.

STREAMS AND LAKES
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Avian Island has several ephemeral freshwater ponds of up to 10,000 m2 and of about 40 cm in depth, the largest being on the eastern coast, at about 5 m altitude, and on the north-western coast near sea level. Numerous small pools and meltwater channels develop from seasonal snow melt, and small streams drain valleys in the vicinity of the ponds. Both the ponds and melt-pools freeze solid in winter. Freshwater bodies on the island are organically enriched by guano, a source of nutrients, and in summer a number of the ponds show a rich benthic flora and fauna of algae, phyllopods, copepods, Nematoda, Protozoa, Rotifera, and Tardigrada. Large numbers of the crustacean Branchinecta sp. have also been observed (Poncet and Poncet 1979). The freshwater ecology of the island has not been studied in detail.

BREEDING BIRDS
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Seven species of birds breed on Avian Island, which is a relatively high number compared to other sites on the Antarctic Peninsula. Several species have unusually high populations, being some of the largest for their species in the Antarctic Peninsula region (Map 3). Detailed year-round data for all species were collected in 1978-79 (Poncet and Poncet 1979), while data are otherwise sporadic. Descriptions below are thus often based on a single season’s observations and it should be emphasised that these data are therefore not necessarily representative of longer term population trends. However, this is the best information that is presently available.
The most recent data available for Adélie penguins (Pygoscelis adeliae) on Avian Island indicated a population of 35,600 breeding pairs (11/11/78) (Poncet and Poncet 1979, Woehler 1993). The colony occupies the northern half and central eastern coast of the island (Map 3). The former management plan referred to the Avian Island colony as “the largest on the Antarctic Peninsula [containing] a third of the total population breeding in the region”. While this is not substantiated by recent data (e.g. one Antarctic Peninsula colony has over 120,000 pairs and several others have over 30,000 (Woehler 1993)), the Avian Island colony represents one of the largest breeding populations in this region. It contains perhaps as much as 9% of the total Adélie breeding population along the Antarctic Peninsula, excluding the South Shetland Islands.
In 1978-79 Adélie penguins were recorded on the island from October until the end of April, with egg laying occurring through October and November, and the first chicks hatching around mid-December. Chick créches were observed around mid-January, with the first chicks becoming independent near the end of January. Most of the moulting adults and independent chicks had departed the island by the third week of February, although groups returned periodically throughout March and April.
A large colony of blue-eyed cormorants (Phalacrocorax atriceps) has been recorded in three groups located on the south-western coastal extremity of the island (Map 3). Stonehouse (1949) reported about 300 birds present in October 1948; a similar number were recorded in mid-November 1968, most of which were breeding (Willey 1969). Poncet and Poncet (1979) observed 320 pairs in 1978, and approximately 670 pairs on 17 January 1989 (Poncet 1990). A count on 23 February 2001 recorded 185 chicks, although it is probable some had departed by the time of the count; approximately 250 nest sites were counted. In 1968 blue-eyed cormorants were observed present on the island from 12 August, with egg laying occurring from November, and chicks hatching in December (Willey 1969). In 1978-79 they were observed from September until June, with egg laying occurring from November through to January, when the first chicks hatched, and chicks started to become independent in the third week of February (Poncet and Poncet 1979) .
Of the thirteen southern giant petrel (Macronectes giganteus) colonies known south of the South Shetland Islands, Avian Island is one of the two largest, and comprises about one fifth of the breeding population in the southern Antarctic Peninsula region (Patterson et al in press). In 1979 the southern giant petrels occupied principally the elevated rocky outcrops of the central and southern half of the island in four main groups (Map 3). Data on the numbers of birds present on the island are shown in Table 1.
Table 1: Southern giant petrel (Macronectes giganteus) numbers at Avian Island.

Year Number
of birds		 Number
of pairs		 Number
of chicks		 Source
1948 ~100 n/a n/a Stonehouse 1949
1965 n/a 160 n/a Patterson et al 2000 (?)
1968 400 163 n/a Willey 1969
1979 n/a 197 n/a Poncet and Poncet 1979
1989 n/a 250 n/a Poncet 1990
2001 n/a n/a 237 Harris 2001

n/a - not available.

In 1978-79 the birds were present on Avian Island from mid-September through to as late as June. In this season, egg laying occurred from late October through to the end of November, with hatching occurring throughout January and chicks generally achieving independence by April. In the 1978-79 austral summer up to 100 non-breeders were observed on the island during the courtship period in October, with these numbers decreasing to a few non-breeders as the season progressed.
Approximately 200 adult Kelp gulls (Larus dominicanus), of which over 60 pairs were breeding, were recorded on Avian Island in 1978-79. These birds were distributed widely, but principally in the elevated central and southern parts of the island (Poncet and Poncet 1979) (Map 3). In the 1978-79 austral summer the majority of breeders arrived in early October, followed by egg laying around mid-November and hatching a month later. Detailed data are not available because of concern that human disturbance by data collection would seriously impair the breeding performance of this species. However, no more than 12 chicks were observed on the island near the end of January 1979, which would suggest breeding performance in this season was low: the exact cause – whether human disturbance or natural factors – could not be determined. In 1967, 19 pairs and 80-120 birds were recorded (Barlow 1968).
An estimate of at least several hundred pairs of breeding Wilson’s storm petrels (Oceanites oceanicus) on the island was made in 1978-79 (Poncet and Poncet 1979). Wilson’s storm petrels were observed on the island from the second week of November, with laying and incubation probably occurring through to mid-December. Departure of adults and independent chicks was largely complete by the end of March. Most of the rocky outcrops on the northern half of the island and all of the stable rocky slopes in the south are ideal habitat for this species.
In 1978-79 about 25-30 pairs of south polar skuas (Catharacta maccormicki) were breeding on Avian Island. The skua nests were distributed widely over the island, although the majority were on the central and eastern part of the island, especially on slopes overlooking the Adélie penguin colony (Map 3). Large groups of non-breeders (around 150 birds; Poncet and Poncet 1979) were observed to congregate around the shallow lake on the eastern side of the island. Barlow (1968) reported approximately 200 non-breeding birds in 1968. In the 1978-79 austral summer the south polar skuas took up residence around the end of October, with egg laying in early December and hatching complete by the end of January. Independent chicks and adults generally departed by the end of March, with some late-breeders remaining until mid-April. A breeding success of one chick per nest was reported in the 1978-79 austral summer. Barlow (1968) reported 12 breeding pairs of brown (=subantarctic) skuas (Catharacta loennbergi), although this number could include south polar skuas. One breeding pair of brown skuas was recorded on the southwest of the island in the 1978-79 austral summer.
This is the southernmost record of this species breeding along the Antarctic Peninsula. Several non-breeding brown skuas were also recorded in the same season.
Several other bird species, known to breed elsewhere in Marguerite Bay, are frequent visitors to Avian Island, notably Antarctic terns (Sterna vittata), snow petrels (Pagodroma nivea), and southern fulmars (Fulmarus glacialoides). These species have not been observed to nest on Avian Island. Small numbers of Antarctic petrels (Thalassoica antarctica) have been seen on a few occasions. The cape petrel (Daption capense) was observed on Avian Island in October 1948 (Stonehouse 1949). Solitary individuals of king (Aptenodytes patagonicus) and chinstrap (Pygoscelis antarctica) penguins were observed in 1975 and 1989, respectively.

TERRESTRIAL BIOLOGY
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Vegetation on Avian Island is generally sparse, and the flora has not been described in detail. Phanerogams are absent from the island and there is a limited range of cryptogams, although there is a rich lichen flora. To date, nine moss and 11 lichen species have been identified within the Area.
Mosses described are Andreaea depressinervis, Brachythecium austro-salebrosum, Bryum argenteum, B. pseudotriquetrum, Pohlia cruda, P. nutans, Sanionia uncinata (=Drepanocladus uncinatus), Syntrichia princeps (=Tortula princeps) and Warnstorfia laculosa (=Calliergidium austro-stramineum). The latter species is at the southern limit of its known range on Avian Island (Smith 1996). Moss development is confined to those parts of the island that are unoccupied by breeding Adélie penguins or blue-eyed cormorants, and occurs in moist depressions or by melt pools. Patches of moss of up to 100 m2 surround the shore of a small pond on the hill in the south of the Area, at ca. 30 m elevation. The green foliose alga Prasiola crispa is widespread in wet areas of the island.
Lichens identified on Avian Island are Acarospora macrocyclos, Cladonia fimbriata, C. gracilis, Dermatocarpon antarcticum, Lecanora dancoensis, Lecidea brabantica, Physcia caesia, Rinodina egentissima, Siphulina orphnina, Thamnolecania brialmontii, and Usnea antarctica. The most extensive communities are on the rocky outcrops in the south of the island.
The microinvertebrate fauna, fungi and bacteria on Avian Island have yet to be investigated in detail. Thus far only one mesostigmatid mite (Gamasellus racovitzai) (BAS Invertebrate Database 1999) has been described, although a Collembollan (springtail) and several species of Acari (mites) have been observed but not identified (Poncet 1990). A number of nematode species (dominated by Plectus sp.) (Spaull 1973) and one fungus (Thyronectria hyperantarctica) (BAS Invertebrate Database 1999) have been recorded on the island.

BREEDING MAMMALS AND MARINE ENVIRONMENT
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Weddell seals (Leptonychotes weddellii) were common on and around Avian Island in 1978-79. During the winter more than a dozen remained, hauled out on coastal ice (Poncet 1990). Several pups were born on the shores of the island in the last week of September 1978. An elephant seal (Mirounga leonina) was reported pupping on the northeastern coast of Avian Island on 10 October 1969 (Bramwell 1969). Aerial photography taken on 15 December 1998 revealed 182 elephant seals hauled out in groups, mostly close to the ponds. Leopard seals (Hydrurga leptonyx) have been observed around the shoreline, and one was observed ashore in winter 1978. A number of non-breeding Antarctic fur seals (Arctocephalus gazella) were reported on the island in March 1997 (Gray and Fox 1997), and again at the end of January 1999 (Fox pers comm 1999). At least several hundred were present on 23 February 2001 (Harris 2001), particularly on beaches and low-lying ground in the central and northern parts of the island. Crabeater seals (Lobodon carcinophagus) are regularly seen in Marguerite Bay, but have not been reported on Avian Island. The marine environment surrounding Avian Island has not been investigated.

HUMAN ACTIVITIES / IMPACTS
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Human activity at Avian Island has been sporadic. The first record of a visit was made in October 1948, when members of the UK Stonington Island expedition discovered the large Adélie penguin colony on Avian Island (then referred to as one of the Henkes Islands). Subsequent visits have comprised a mixture of science, base personnel recreation, tourism and logistic activity (survey etc.). Refuges were constructed on the island in 1957 and 1962 by Argentina and Chile respectively (see Section 6(iii)).
A geological field party of two camped for about 10 days on the southeast of the island in November 1968 (Elliott 1969). In the same year, a UK Naval hydrographic survey team camped on the eastern coast of Avian Island over the summer. Permanent chains and rings for mooring lines to the survey vessel were installed in a small bay on the northwestern coast, and were still present in 1989 (Poncet 1990).
In 1969, a field party camped on the island for a month conducting research on the common cold virus: accompanying dogs were inoculated with a virus and then returned to base (Bramwell 1969). Dogs often accompanied personnel on the regular visits to Avian Island during the period of operation of the UK base on Adelaide Island, but impacts are unknown.
A two-person party spent a year on the island in 1978-79, based on the yacht Damien II, making detailed observations of the avifauna and other aspects of the biology and natural environment of the island (Poncet and Poncet 1979, Poncet 1982, Poncet 1990). The yacht was moored in a small cove on the NW coast. This yacht party regularly visited the island over the next decade before SPA designation.
Map survey work and aerial photography was conducted on and over the island in 1996-98 (Fox and Gray 1997, Gray and Fox 1997), and 1998-99 (Fox pers. comm.1999).
The impacts of these activities have not been described and are not known, but are believed to have been relatively minor and limited to transient disturbance to breeding birds, campsites, footprints, occasional litter, human wastes, scientific sampling and markers. Despite the likely transient nature of most disturbance, it has been reported that human visits have caused loss of eggs and chicks, either through nest abandonment or by opportunistic predation. Several species, such as southern giant petrels and kelp gulls are particularly vulnerable to disturbance, and have been observed to abandon nests at particular periods of the nesting cycle, perhaps at the sight of people as much as 100 m distant (Poncet 1990). Approximately 140 people, including a tour vessel of 100, were reported to have visited Avian Island in the 1989-90 summer. Growing concern over the number and unregulated nature of visits prompted SPA designation.
The most lasting and visually obvious impacts are associated with the two refuges and beacon structures described in Section 6(iii), which are situated close to breeding birds. Both refuges were in poor repair in February 2001, with rubbish such as rusting cans, glass, wood, roofing iron and empty fuel drums nearby. Birds and seals were observed among this rubbish in February 2001. The older of the two beacon structures is disused and its iron structure, while standing, is rusting and deteriorating. The new beacon, erected in February 1998, was in good repair in February 2001.