St. Margaret's Island
Climate exposure
This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.
Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.
Geology & landscape
Mining / Industrial: Quarry · Geological Period: Carboniferous · Rock Type: Carboniferous Limestone, Limestone
Landscape processes: Coastal
Birds & fish recorded
Birds
| Species | Season |
|---|---|
| cormorant | Breeding |
| great black-backed gull | Breeding |
| guillemot | Breeding |
| herring gull | Breeding |
| kittiwake | Breeding |
| lesser black-backed gull | Breeding |
| puffin | Breeding |
| razorbill | Breeding |
Description
Description A seabird breeding island supporting a nationally important cormorant colony with about 3% of the British population. St Margaret’s Island, connected to the north-western corner of Caldey Island at low water, is composed of Carboniferous Limestone rocks. Small stacks occur on the extensive rocky foreshore at the eastern end. The level 30 metre plateau surface of the island is broken by a disused quarry, which nearly isolates the eastern point. Maritime grassland, heavily modified by seabirds and by sheep grazing and other past agricultural practices, dominates the plateau surface. As early as 1603, George Owen wrote that the island “beareth good grass for sheep and rabbits, and store of gulls”. The steep cliffs support some crevice vegetation with golden-samphire Inula crithmoides and rock samphire Crithmum maritimum. Notable plants include abundant tree-mallow Malva arborea which the Cambridge botanist, the Rev John Ray, found “in great plenty” on St Margaret’s in 1662. The cormorant colony is the largest in Wales and amongst the largest in Britain. About 200 pairs have regularly nested since 1969. Over 100 pairs were present in 1927 and the peak count of 322 pairs was reached in 1973. The colony has been well studied, especially after 1967, and at least 3000 young cormorant have been ringed. By 1985 some 70% of the adults carried rings and about 400 ring recoveries had been achieved. Breeding seabirds in 1985 included 238 cormorant, 383 kittiwake, 111 razorbill, 3 puffin, 13 shag, 44 great black-backed gull, 108 herring gull and 10 lesser black-backed gull pairs. 432 individual guillemot were present in 1985. Herring and great black-backed gulls have declined dramatically since the late 1970s. Remarks: The site lies within the Pembrokeshire Coast National Park
Species mentioned
Show the 12 species mentioned in the description, with red-list status| English name search for this in other sites |
Latin name search with Google |
IUCN / Red List | Type | Family |
|---|---|---|---|---|
| razorbill | Alca torda | LC (Breeding) | bird-auk | alcidae |
| puffin | Fratercula arctica | CR (Breeding) | bird-auk | alcidae |
| guillemot | Uria aalge | LC (Breeding) | bird-auk | alcidae |
| shag | Gulosus aristotelis | VU (Breeding) | bird-frigate | fregatidae |
| cormorant | Phalacrocorax carbo | NT (Breeding) | bird-frigate | fregatidae |
| herring gull | Larus argentatus | EN (NonBreeding), EN (Breeding) | bird-gull | laridae |
| lesser black-backed gull | Larus fuscus | DD (Breeding) | bird-gull | laridae |
| great black-backed gull | Larus marinus | EN (NonBreeding), CR (Breeding) | bird-gull | laridae |
| kittiwake | Rissa tridactyla | EN (Breeding) | bird-gull | laridae |
| rock samphire | Crithmum maritimum | LC | herb | apiaceae |
| golden samphire | Inula crithmoides | Not listed in GB list | herb | asteraceae |
| tree mallow | Malva arborea | LC | herb | malvaceae |