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Site description (2006 baseline):
Site location and context
The Jasons are a group of remote islands, to the far
north-west of West Falkland. Some are scenically spectacular,
with cliffs and craggy peaks, while others are low lying and
covered with Tussac.
Steeple Jason is a large island, 5 miles (8 km) long, running
south-east to north-west with an average width of around
0.6 miles (1 km). The island is divided into two main
sections by a narrow neck, which marks the only break in a
ridge of hills with steep slopes on both sides. The island
peaks at 263 m towards the north and again at 290 m
towards the south. At the northern point a wide, low plateau
forms an important area for breeding colonial seabirds,
which extend, in more scattered colonies, along the southern
steep coastlines. The main stands of Tussac are along the
southern shorelines and extend from around 30 m to the
highest points of the island. Scattered patches of Tussac also
exist in the centre of the island and there is a large stand in
the middle of the northern half on the eastern coast.
Grand Jason is the largest of the group and has a similar
history of stocking to Steeple Jason. The terrain varies from
steep cliffs and high plateaux with gullies to Tussac-covered
west-facing and south-facing slopes. There are severely
eroded areas of ‘black ground’, particularly at the northern,
south-eastern and western extremities. The island’s peak is
at 361 m and Tussac is sparse above 60–90 m, with low
grasses and small cushion plants.
Steeple Islet is a small island, generally low lying, with
boulder beaches and low cliffs, sloping towards a rocky
north-western point. Almost the entire island is covered in
dense Tussac grass, which has apparently never been grazed.
Flat Jason is a low-lying Tussac island with vertically
dipping rock strata, and is possibly the largest island in the
Falklands archipelago that has not been grazed, partly due
to the difficulties of access. The island is almost 3.7 miles (6
km) long on a north-west to south-east axis, with an average
width of some 600 m. At the centre of the island there is a
narrow neck with a boulder beach that may sometimes be
tidally inundated. The northern coasts are mainly boulder
beaches with rocky outcrops, while the southern shores are
more formidable, with steep-sided mini stacks and cliffs.
Elephant Jason has a long ridge rising to a height of 208 m,
sloping into low-lying plateaux thickly covered with dense
Tussac on the northern and eastern coasts, and with sheer
cliffs on the western coast. The fringe of Tussac extends
around most of the island, giving way at the northernmost
point to areas of grass and heath. For a short time early in
the 20th century Elephant Jason was used as a base for
government sealing inspectors, who constructed a shanty on
the island. The remains of the cast iron stove can still be
seen.
South Jason is a long, narrow island, running almost due
east–west and reaching over 4.3 miles (7 km) in length and
only 0.6 miles (1 km) wide at its widest point. The entire
island has a central ridge reaching around 300 m in height,
flattening out to the east and west. The eastern point has a
dense cover of Tussac, while the western point is drier, with
sparse grassland and a small pond. The southern slopes are
mostly covered with dense Tussac while the northern slopes
are rocky, and the vegetation consists of dry upland heath,
with Balsam-bog Bolax gummifera and exposed rock layers.
South Fur is a small island lying around 3 miles (5 km) off
the south coast of Steeple Jason. Just 0.6 miles (1 km) long
and 300 m wide, its highest point is only 18 m. Unusually, it
is composed mainly of large blue-grey dolerite boulders,
with a dense but low Tussac covering. It has not been
stocked with sheep or cattle.
North Fur lies north-east of Flat Jason and is difficult to
access due to steep cliffs formed from vertically bedded
rocks. It is heavily overgrown with dense and tall Tussac,
and has small amounts of Wild Celery Apium australe,
Stonecrop Crassula moschata and Swordgrass Carex trifida, but
it has never been stocked, probably because access is difficult.
‘Clarke’s Islet’ lies about 0.3 miles (0.5 km) off the
north-eastern coast of Grand Jason. It is a rugged low
island with many rock outcrops, patches of ‘black ground’
and open low Tussac, heavily used by Southern Sea Lions.
The Fridays are two small islands situated around 3 miles
(5 km) from the north-west coast of Flat Jason. Both are low
lying, and consist of large coastal rocky strike ridges with
Tussac between. On the larger of the two, this area gives
way in the centre to open peaty ground, which is the site of
a colony of Southern Giant Petrels. Southern Sea Lions use
both islands.
On Steeple Jason in October and November 1997, 36
species were noted, with 27 probably breeding, and 39
species were recorded on Grand Jason with 30 of them
almost certainly breeding. A total of 12 species, 11 probably
breeding, were found on Steeple Islet during a visit of only
90 minutes. Clarke’s Islet held only 10 species, almost all
breeding and including Cobb’s Wrens, Tussacbirds and
Canary-winged/Black-throated Finches. On Flat Jason, 32
species were seen, with 26 probably breeding. On Elephant
Jason, 33 species were noted, of which 30 were probably
breeding. Populations of Thin-billed Prions, Wilson’s
Storm-petrels, Grey-backed Storm-petrels, Rock Shags and
Imperial Shags warrant further investigation.
Endemic sub-species present are the Common Diving-petrel,
Black-crowned Night-heron, Upland Goose, Short-eared Owl,
Dark-faced Ground-tyrant, Falkland Grass Wren, Falkland
Thrush and the Long-tailed Meadowlark. The Falkland Pipit
is apparently absent from all islands in this extreme
western group.
Non-bird biodiversity: The presence of breeding Southern Elephant Seal, Southern
Sea Lion and South American Fur Seal has been confirmed
on most of the islands in the group. About 200 Southern
Sea Lion pups are born annually in the archipelago and
there are many non-breeding adults and sub-adults. Islands
Criteria Key species Number of Notes
breeding
pairs (if
known)
A1, A4ii Black-browed Albatross 213,800 Largest Falkland colony is on Steeple Jason
Thalassarche melanophrys
A1, A4ii Gentoo Penguin 12,300 Steeple and Grand Jason only
Pygoscelis papua
A1, A4ii Rockhopper Penguin 142,000 Steeple, Grand and Elephant Jason only
Eudyptes chrysocome
A1, A4ii Southern Giant-petrel 1,500 Main colonies on Grand and Steeple Jason, small
Macronectes giganteus colony on The Fridays
A1 Magellanic Penguin Numerous Breeding on Grand, Steeple, Flat and Elephant
Spheniscus magellanicus Jason and North Fur, no counts
A1 Macaroni Penguin 10 Maximum count
Eudyptes chrysolophus
A1, A2, A4ii Striated Caracara 250 Jason Group are the Falkland stronghold of this
Phalcoboenus australis species
A1, A2 Cobb’s Wren Numerous All islands except Steeple Jason
Troglodytes cobbi
A2 Ruddy-headed Goose 10 Few pairs on Grand and Steeple Jason only
Chloephaga rubidiceps
A2 Canary-winged/Black-throated Finch On all islands in group, not counted
Melanodera melanodera
A2 Falkland Steamer Duck All islands except Clarke’s, not counted
Tachyeres brachypterus
A2 Tussacbird/Blackish Cinclodes All islands in group, not counted but numerous
Cinclodes antarcticus
A4iii Combined seabirds >369,850
Key species
123
where breeding occurs are Steeple Jason (46 pups), Fridays
(29), Flat Jason (17), Elephant Jason (26), South Jason (5)
and South Fur (4). South American Fur Seals breed on
Jason West Cay (2,000) and East Cay (2,000), Seal Rocks
(200), Elephant Jason (200) and North Fur (33 pups).
At least 43 flowering plant species occur including six
endemics: Coastal Nassauvia Nassauvia gaudichaudii, Vanilla
Daisy Leucheria suaveolens, Lady’s Slipper Calceolari
fothergillii, Woolly Falkland Ragwort Senecio littoralis,
Smooth Falkland Ragwort Senecio vaginatus and Falkland
Rockcress Phlebolobium maclovianum. The most surprising
plant found on Grand Jason was an unidentified purslane
(Calandrinia), possibly a new endemic plant.
Pressure/threats to key biodiversity
Steeple and Grand Jason were stocked with cattle and up to
5,000 sheep from the late 19th century to about 1968. In
1970, after all the sheep had been removed, the islands
were bought by Len Hill of Birdland, UK, to safeguard the
habitat. Since then, some regeneration of the vegetation has
occurred. Ownership recently passed to the Wildlife
Conservation Society of New York (WCS). In 2002 a fire
broke out on Steeple Jason as a result of dry weather and a
lightning strike. This was contained to a narrow gully in
the southern slopes of the northern half of the island and
continued to burn, although control measures were taken
to ensure that it did not spread to the albatross colonies.
The fire was thought to be totally extinguished by May
2003. Elephant Jason was stocked briefly in 1967 when the
Falkland Islands Government leased it for grazing of
several hundred sheep. These were removed in 1971 and
the island has not been grazed since.
South Jason was accidentally burnt in 1960 and the fire
continued burning into the peat for several months. In
2001, a fire was caused on the northern coast by the
detonation of unexploded ordnance from the remains of a
military plane that had crashed in 1982. The fire burnt
through most of the Tussac on the southern slope, but the
level of damage is not known as the numbers of burrowing
birds and songbirds had never been recorded. There is
evidence that a severe fire affected the island in 1949 and
traces of this were still visible in the 1980s, having left
much of the north-western side of the island devoid of
vegetation and prone to erosion. Government permits to
visit South Jason include a strong warning of the fire risk.
In order to minimise this, visits should take place only
between May and July.
All the government-owned islands were made Crown
Reserves in July 1950, declared as wild animal and bird
sanctuaries in May 1966, and reclassified as National Nature
Reserves in 1999. Many of the islands are in their original
state with dense Tussac and other natural vegetation.
The flora and fauna of the Jasons urgently need a full
survey of species present and abundance. The remoteness
of these islands from Stanley and the difficulties of access
have meant that, in the past, it was impossible to make
basic biological surveys. The research station constructed in
2003 on Steeple Jason by the WCS should facilitate longterm
ecological studies. WCS and Falklands Conservation
are currently developing a management plan for Grand
and Steeple Jason.
Overgrazing has left large parts of Steeple and Grand Jason
badly eroded. A Tussac replanting programme could
improve the habitat for birds, though the logistics would be
difficult. On other islands in the group, Tussac is still
mostly dominant, except on the higher parts of Elephant
Jason, where heathland predominates.
Steeple and Grand Jason, the two largest islands in this
archipelago, are becoming a popular tourist destination for
cruise ships. It is very important that the Falkland Islands
Countryside Code is followed,
particularly to guard against the risk of fire. The islands in
this group are free of introduced predators, with the
exception of Steeple Jason, which has a feral population of
House Mice Mus musculus. This probably explains the
absence of territory-holding Cobb’s Wrens and poses a
threat to other passerines and ground-nesting species,
which would benefit from the eradication of mice. All
visitors should be informed about the dangers of
accidentally introducing alien species to the islands.
Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Jason Islands Group (Falkland Islands (Malvinas)). Downloaded from
https://datazone.birdlife.org/site/factsheet/jason-islands-group-iba-falkland-islands-(malvinas) on 23/12/2024.
