The number of species of land birds in Scilly is also small. Visitors to the islands are usually surprised to find many common passerines, let alone owls and woodpeckers, missing or in very low numbers. Equally the very confiding nature of blackbirds Turdus merula and song thrushes T. philomelos will soon be remarked on. The Isles of Scilly have hardly any land mammals, and no predators such as foxes Vulpes vulpes or stoats Mustela erminea. There are no snakes and very few resident species of butterflies or dragonflies; this is common for all groups. But on the other hand there are species that are only found in Scilly, such as the Scilly shrew Crocidura suaveolens cassiteridum, several rare lichens and many other examples of interesting and uncommon species.
Lusitanian and Mediterranean influences
References will be made in the following chapters to Lusitanian influences. The geographical position of the Isles of Scilly has led to a number of unique aspects of the flora and fauna. Many species are at their northern limit in Scilly and southwestern Britain. These are species from the Atlantic coastal regions of southern Europe, based on the former Roman province of Lusitania, and into the Mediterranean. A visit to parts of Spain or Portugal will reveal many species of plants that are commonly seen in Scilly, but that are rare of absent from the rest of Britain. There are also lichens, invertebrates and other groups with Lusitanian species that reflect the same distribution, and in the marine environment many species found in southern or Mediterranean waters that also occur in the Isles of Scilly and the Channel Islands. In the New Atlas of the British and Irish Flora (Preston et al., 2002) the floristic elements of the flora are described: the Mediterranean-Atlantic and Submediterranean-Subatlantic are plants that are associated with these biogeographical regions.
NATURE CONSERVATION DESIGNATIONS
Currently the Isles of Scilly are covered by a plethora of designations relating in some way to nature conservation.
The whole coastline of the Isles of Scilly was designated a Heritage Coast in 1974.
Scilly is a candidate Special Area of Conservation (cSAC) under the European Habitats Directive.
A Special Protection Area (SPA) (for birds) covers 4.09km2.
Scilly is a Ramsar site, an international important-wetland designation.
Scilly was designated a Conservation Area in 1975.
Twenty-six sites have been designated Sites of Special Scientific Interest (SSSI) by English Nature. Of these five are geological sites.
The Isles of Scilly has been a Voluntary Marine Park since 1987 – this includes the whole area within the 50m depth contour line.
Scilly was designated an Area of Outstanding Natural Beauty (AONB) in 1975 – it includes ‘all the islands and islets above mean low water that together form the Isles of Scilly’. The total area covered is 16km2. Scilly is the smallest AONB in the country; also the only one under a single local authority. The Management Plan for the AONB was published in 2004.
STUDYING THE FLORA AND FAUNA OF THE ISLES OF SCILLY
Although many of the visitors to the Isles of Scilly over the centuries have commented on the natural history of the islands, most of what has been written has concentrated on the most obvious groups. Authoritive books have covered plants, birdlife, butterflies and moths, but many of the marine species, insects and more difficult groups are the subject of papers in scientific journals or rather inaccessible unpublished reports held by English Nature and other bodies. Recently there has been a resurgence of interest in these other groups, especially invertebrates and marine life, which had otherwise been left to a small number of specialists.
For many years botanists have been well served by a Flora (Lousley, 1971), but it is now due for an update as there is a great deal of new botanical information available. Some plant hunters whose aim is to record rare plants, and especially alien species, are regular visitors to the islands.
Birds have tended to attract the lion’s share of attention since the late 1950s, when the St Agnes Bird Observatory became a focus for birdwatchers hoping to see rare and unusual migrant and vagrant species. October is still the most popular month for birdwatchers to visit Scilly. This is an extraordinary phenomenon; it has to be seen to be believed. Hundreds of enthusiasts, bristling with telescopes, pagers and binoculars, arrive in Scilly intent on seeing rare migrant birds. These birders mostly have well-defined patterns of behaviour, usually travelling en masse to wherever there is news of some exciting bird. So it is not unusual to see them all gathered in one place, behind lines of telescopes waiting patiently for a glimpse of their quarry. In the evenings many will attend the ‘count’, when the tally of the day’s finds are recorded.
The marine habitat might seem to be rather neglected. Although there are organised field trips to Scilly to study marine ecology, most of the information stays in student dissertations. But for every child visiting the islands half the fun is exploring rock pools. Now, with plenty of opportunities to dive or snorkel, the underwater life is becoming much better known. Underwater safaris, glass-bottomed boats and swimming with seals and seabirds are making this fascinating medium much more accessible to the general public.
Some of these visitors to Scilly are going to take more than a casual interest in what they see. Hopefully they will contribute records and notes that will lead to further expansion of our knowledge of the natural history of the islands. Since its inception the Isles of Scilly Bird Group has produced a report that also includes notes, short papers and reports on natural history subjects other than birds – the Isles of Scilly Bird & Natural History Review. Perhaps this book too will encourage an interest in the fascinating natural history of the Isles of Scilly.
The chapters that follow are arranged to give an overview of the geology, something of the history, the people who contributed to our knowledge of the natural history of the islands, the individual islands, the main habitats, and the major groups of flora and fauna. Descriptions of some of the plant communities are included as an appendix.
CHAPTER 2 Geology and Early History
There are signs of Bronze Age man on every island in Scilly.
Charles Thomas (1985)
GEOLOGY
AT FIRST GLANCE the Ordnance Survey’s geological map of the Isles of Scilly appears to be something of a disappointment: almost the whole of the land shown on the map is coloured in the same shade of red-brown, representing granite. A granite batholith, the Cornubian batholith, extends as a series of cupolas or bosses along the Southwest Peninsula from Dartmoor to Land’s End and the Isles of Scilly, ending at the undersea mass of Haig Fras 95km further on and slightly out of line, presumably due to faulting (Edmonds et