Crow's Nest

Site of Special Scientific Interest · 50.5033, -4.4475

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Cornwall County

Condition (Natural England)

Unfavourable Declining (2)
UnitFeatureConditionArea (ha)Assessed
SX263699 — Unfavourable Declining 6.51 2018-03-20
SX269698 — Unfavourable Declining 12.41 2018-03-20

Habitats

Bracken scrub, Calaminarian grassland, Fast flowing river and stream, Mixed scrub, Montane scrub

Geology & landscape

Mining / Industrial: Copper Mine, Mine Spoil · Rock Type: Granite

Landscape processes: Volcanic / Igneous

Description

Crow’s Nest SSSI Description Crow’s Nest is located on the south-east side of Bodmin Moor and is of special interest for its lower plants. Much of the site occupies a small valley in the headwaters of the River Seaton catchment on the edge of the Bodmin Moor granite. The valley and adjacent hillsides are traversed by a series of east-west trending mineral lodes, rich in copper, and some tin ores. Copper mining here dates from about 1830 and continued for over 50 years leaving behind a legacy of old mine buildings, shafts, adits, mine spoil tips, a disused railway and tramways. The mine spoil tips, associated mine buildings, tracks and the stream banks support a specialised flora of rare mosses and liverworts which are tolerant of the high levels of toxic metals, particularly copper. This contamination has severely restricted the growth of vascular plants, favouring colonisation by specialised mosses and liverworts. To date a total of three nationally rare mosses, three nationally rare liverworts and one nationally scarce liverwort have been recorded at Crow’s Nest. Of particular importance is the occurrence of several colonies of Cornish path-moss Ditrichum cornubicum, a nationally rare species, protected under Schedule 8 of the 1981 Wildlife and Countryside Act (as amended) and listed in the UK Steering Group Biodiversity Report 1995 as a globally threatened/declining species. The total World population of this moss is restricted to copper-rich mine waste at two Cornish sites, Crow’s Nest and a site near to Minions on the north side of Caradon Hill. Cornish path-moss was first discovered in 1963 and was described as a species new to science in 1976. This is a pioneer species of bare or sparsely vegetated mine waste, and at Crow’s Nest occurs on a variety of substrates, including track edges, stream banks and crevices in walls. Two other nationally rare mosses found at Crow’s Nest are Pohlia andalusica and Scopelophila cataractae. The former moss has a sparse distribution in Britain with the majority of its British population being confined to metalliferous mine waste. Scopelophila cataractae, a moss also tolerant of heavy metal contamination, has most of its British population confined to Cornwall. Crow’s Nest is also important for liverworts of the genus Cephaloziella. Three national rarities and one nationally scarce species have been recorded here. Of those which are nationally rare Cephaloziella nicholsonii is a British endemic, the majority of its population being confined to Cornwall. Cornwall also holds a large proportion of the British population of Cephaloziella massalongi with Crow’s Nest supporting the most abundant population in east Cornwall. Both C. nicholsonii and C. massalongi appear to be strictly confined to copper-rich substrates and are particularly abundant on the banks of the stream. The small population of Cephaloziella calyculata at Crow’s Nest represents the first record for east Cornwall. The nationally scarce liverwort Cephaloziella stellulifera also occurs here; its main British populations are concentrated in Cornwall, which a few sites in Devon and Wales. The site also supports a number of mosses and liverworts that are classified as sub-Atlantic and western British. The Atlantic elements of Britain’s bryophyte flora are of international importance and are particularly well represented in western Britain. Characteristic species include the liverwort Lejeunea lamacerina which is a strictly Atlantic species and the western British liverwort Scapania compacta. Sub-Atlantic species recorded here include the mosses Campylopus flexuosus, Hypnum resupinatum and Ptychomitrium polyphyllum together with the following liverworts, Microlejeunea ulicina, Metzgeria temperata and Scapania gracilis. The moss Gymnostomum aeruginosum has only been recorded from three sites in Cornwall including its most recent record here at Crow’s Nest. The stream valley is dominated by high, steep-sided mine spoil tips, almost totally devoid of vegetation apart from lower plants. The valley floor, the flatter tops of the spoil tips and areas where the toxic metals have been leached out, support grassland, bracken and gorse scrub with scattered shrubs and trees, predominantly hawthorn and oak. Remnants of the former landscape of steep slopes covered with granite clitter, bracken, scrub woodland and patchy heathland can still be seen in between the extensive spoil tips and mine workings. Camomile, Chamaemelum nobile, occurs on some of the old tramways. This nationally scarce species has declined dramatically in recent years and Cornwall is now one of its strongholds.

Species mentioned

English name
search for this in other sites		 Latin name
search with Google		 IUCN / Red List Type Family
chamomile Chamaemelum nobile EN herb asteraceae
entire threadwort Cephaloziella calyculata EN liverwort jungermanniales
lesser copperwort Cephaloziella massalongi Not listed in GB list liverwort jungermanniales
greater copperwort Cephaloziella nicholsonii VU liverwort jungermanniales
red heath threadwort Cephaloziella stellulifera NT liverwort jungermanniales
western pouncewort Lejeunea lamacerina LC liverwort jungermanniales
bluish veilwort Metzgeria temperata Not listed in GB list liverwort metzgeriales
fairy beads Microlejeunea ulicina LC liverwort jungermanniales
thickset earwort Scapania compacta LC liverwort jungermanniales
western earwort Scapania gracilis LC liverwort jungermanniales
rusty swan neck moss Campylopus flexuosus LC moss dicranales
Cornish path-moss Ditrichum cornubicum EN moss dicranales
verdigris tufa moss Gymnostomum aeruginosum LC moss pottiales
supine plait moss Hypnum resupinatum Not listed in GB list moss hypnales
gravel thread moss Pohlia andalusica DD moss bryales
greater pin cushion Ptychomitrium polyphyllum LC moss grimmiales
tongue leafed copper moss Scopelophila cataractae EN moss pottiales

Plant communities

A9 — Fast flowing river and stream, Marginal and inundation, Pond ditch and canal, Sluggish river and stream

Potamogeton natans community

Schoenoplectus lacustris, Juncus bulbosus, Sparganium angustifolium, Sparganium erectum, Sparganium minimum, Alisma plantago-aquatica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Elodea canadensis, Lemna minor, Lemna trisulca, Nymphaea alba, Callitriche platycarpa, Callitriche stagnalis, Littorella uniflora, Potamogeton natans, Ranunculus trichophyllus, Glyceria fluitans, Chara subspinosa

A14 — Fast flowing river and stream

Myriophyllum alterniflorum community

Isolepis fluitans, Juncus bulbosus, Fontinalis antipyretica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Lemna minor, Callitriche stagnalis, Littorella uniflora, Potamogeton filiformis, Potamogeton gramineus, Potamogeton natans, Ranunculus peltatus, Chara spp., Nitella hyalina

A17 — Chalk river and stream, Fast flowing river and stream

Ranunculus penicillatus ssp. pseudofluitans community

Berula erecta, Nasturtium officinale, Elodea canadensis, Lemna minor, Callitriche stagnalis, Veronica beccabunga, Polygonum amphibium, Polygonum hydropiper, Potamogeton crispus, Potamogeton pectinatus, Ranunculus penicillatus ssp. pseudofluitans

A18 — Fast flowing river and stream

Ranunculus fluitans community

Fontinalis antipyretica, Fontinalis squamosa var. curnowii, Myriophyllum alterniflorum, Myriophyllum spicatum, Elodea canadensis, Mentha aquatica, Lemna gibba, Lemna minor, Potamogeton perfoliatus, Ranunculus fluitans, Glyceria fluitans, Phalaris arundinacea

OV37 — Calaminarian grassland

Festuca ovina-Minuartia verna community

Calluna vulgaris, Carex caryophyllea, Carex flacca, Bryum pallens, Pohlia nutans, Dicranum scoparium, Rhytidiadelphus squarrosus, Weissia controversa, Cladonia arbuscula, Cladonia chlorophaea, Cladonia furcata, Cladonia gracilis, Cladonia portentosa, Cladonia pyxidata, Cladonia rangiformis, Coelocaulon aculeatum, Parmelia saxatilis, Achillea millefolium, Cirsium vulgare, Jacobaea vulgaris, Pilosella officinarum, Noccaea caerulescens, Campanula rotundifolia, Cerastium fontanum, Minuartia verna, Anthyllis vulneraria, Lotus corniculatus, Trifolium repens, Geranium robertianum, Thymus praecox, Linum catharticum, Euphrasia officinalis, Plantago lanceolata, Rumex acetosa, Galium saxatile, Galium sterneri, Viola lutea, Agrostis capillaris, Agrostis stolonifera, Anthoxanthum odoratum, Arrhenatherum elatius, Avenula pratensis, Dactylis glomerata, Festuca ovina, Festuca rubra, Koeleria macrantha

W20 — Montane scrub

Salix lapponum-Luzula sylvatica scrub

Salix arbuscula, Salix cinerea, Salix lapponum, Salix myrsinites, Salix phylicifolia, Salix reticulata, Empetrum nigrum, Calluna vulgaris, Salix lanata, Vaccinium myrtillus, Vaccinium uliginosum, Carex atrata, Carex bigelowii, Carex binervis, Carex flacca, Luzula multiflora, Luzula sylvatica, Huperzia selago, Selaginella selaginoides, Aulacomnium palustre, Mnium hornum, Philonotis fontana, Plagiomnium undulatum, Rhizomnium punctatum, Dicranum bonjeanii, Dicranum majus, Dicranum scoparium, Fissidens adianthoides, Racomitrium lanuginosum, Calliergonell cuspidatum, Ctenidium molluscum, Hylocomium splendens, Hypnum callichroum, Hypnum cupressiforme, Palustriella commutatum, Plagiothecium denticulatum, Plagiothecium undulatum, Pleurozium schreberi, Ptilium crista-castrensis, Rhytidiadelphus loreus, Rhytidiadelphus squarrosus, Rhytidiadelphus triquetrus, Sanionia uncinata, Scorpidium revolvens, Thuidium tamariscinum, Atrichum undulatum, Polytrichastrum alpinum, Sphagnum capillifolium, Sphagnum fallax, Sphagnum girgensohnii, Sphagnum palustre, Sphagnum russowii, Sphagnum squarrosum, Sphagnum subnitens, Sphagnum teres, Barbilophozia barbata, Chiloscyphus polyanthos, Diplophyllum albicans, Lophocolea bidentata, Plagiochila porelloides, Ptilidium ciliare, Scapania undulata, Cladonia squamosa, Peltigera canina, Angelica sylvestris, Caltha palustris, Hieraclium spp., Saussurea alpina, Solidago virgaurea, Campanula rotundifolia, Succisa pratensis, Valeriana officinalis, Rhodiola rosea, Vaccinium vitis-idaea, Thymus praecox, Epilobium anagallidifolium, Dactylorhiza viridis, Euphrasia officinalis, Rhinanthus minor, Oxalis acetosella, Oxyria digyna, Polygonum viviparum, Rumex acetosa, Anemone nemorosa, Ranunculus acris, Thalictrum alpinum, Alchemilla alpina, Alchemilla glabra, Filipendula ulmaria, Geum rivale, Galium boreale, Galium saxatile, Saxifraga aizoides, Saxifraga hypnoides, Saxifraga oppositifolia, Saxifraga stellaris, Viola riviniana, Agrostis canina, Agrostis capillaris, Anthoxanthum odoratum, Deschampsia cespitosa, Deschampsia flexuosa, Festuca ovina, Festuca rubra, Nardus stricta, Dryopteris dilatata, Phegopteris connectilis

W21 — Hedgerow scrub, Mixed scrub

Crataegus monogyna-Hedera helix scrub

Hedera helix, Salix cinerea, Acer pseudoplatanus, Ilex aquifolium, Betula pendula, Corylus avellana, Fagus sylvatica, Quercus robur, Fraxinus excelsior, Malus sylvestris, Sorbus aria, Taxus baccata, Ulmus glabra, Ulmus procera, Sambucus nigra, Viburnum lantana, Euonymus europaeus, Cornus sanguinea, Juniperus communis, Ligustrum vulgare, Clematis vitalba, Rhamnus cathartica, Crataegus laevigata, Crataegus monogyna, Prunus spinosa, Juncus effusus, Plagiomnium undulatum, Brachythecium rutabulum, Kindbergia praelonga, Rhynchostegium confertum, Tamus communis, Heracleum sphondylium, Torilis japonica, Arum maculatum, Arctium minus, Cirsium arvense, Lonicera periclymenum, Moehringia trinervia, Silene dioica, Stellaria graminea, Stellaria holostea, Stellaria media agg., Calystegia sepium, Mercurialis perennis, Geranium robertianum, Iris foetidissima, Glechoma hederacea, Lamium purpureum, Origanum vulgare, Stachys sylvatica, Teucrium scorodonia, Allium ursinum, Hyacinthoides non-scripta, Circaea lutetiana, Rumex sanguineus, Anemone nemorosa, Ranunculus repens, Fragaria vesca, Geum urbanum, Potentilla sterilis, Poterium sanguisorba, Rosa arvensis, Rosa canina, Rubia peregrina, Rubus fruticosus agg., Galium aparine, Urtica dioica, Viola riviniana, Anisantha sterilis, Arrhenatherum elatius, Brachypodium pinnatum, Brachypodium sylvaticum, Bromopsis erecta, Dactylis glomerata, Elytrigia repens, Holcus lanatus, Holcus mollis, Poa trivialis, Asplenium scolopendrium, Pteridium aquilinum, Dryopteris filix-mas

W22 — Hedgerow scrub, Mixed scrub

Prunus spinosa-Rubus fruticosus scrub

Hedera helix, Acer campestre, Corylus avellana, Ulex europaeus, Prunus spinosa, Plagiomnium undulatum, Brachythecium rutabulum, Eurhynchium striatum, Kindbergia praelonga, Thuidium tamariscinum, Atrichum undulatum, Lophocolea bidentata, Achillea millefolium, Cardamine flexuosa, Lonicera periclymenum, Moehringia trinervia, Silene dioica, Silene uniflora, Stellaria media agg., Mercurialis perennis, Geranium robertianum, Stachys sylvatica, Teucrium scorodonia, Hyacinthoides non-scripta, Oxalis acetosella, Digitalis purpurea, Plantago lanceolata, Veronica chamaedrys, Armeria maritima, Rumex acetosa, Filipendula ulmaria, Geum urbanum, Rosa canina, Rubus fruticosus agg., Rubus idaeus, Galium aparine, Urtica dioica, Viola riviniana, Agrostis capillaris, Brachypodium sylvaticum, Dactylis glomerata, Festuca rubra, Holcus lanatus, Holcus mollis, Poa trivialis, Asplenium scolopendrium, Pteridium aquilinum, Dryopteris borreri, Dryopteris filix-mas

W25 — Bracken scrub

Pteridium aquilinum-Rubus fruticosus underscrub

Hedera helix, Acer pseudoplatanus, Fagus sylvatica, Quercus robur, Fraxinus excelsior, Sambucus nigra, Ulex europaeus, Crataegus monogyna, Prunus spinosa, Luzula multiflora, Mnium hornum, Brachythecium rutabulum, Kindbergia praelonga, Angelica sylvestris, Conopodium majus, Heracleum sphondylium, Arum maculatum, Cirsium arvense, Lonicera periclymenum, Silene dioica, Stellaria holostea, Mercurialis perennis, Geranium robertianum, Glechoma hederacea, Teucrium scorodonia, Hyacinthoides non-scripta, Chamerion angustifolium, Circaea lutetiana, Digitalis purpurea, Rumex acetosa, Anemone nemorosa, Ficaria verna, Potentilla erecta, Rosa arvensis, Rosa canina, Rubus fruticosus agg., Rubus idaeus, Galium aparine, Galium mollugo sens.lat., Galium saxatile, Urtica dioica, Viola riviniana, Agrostis capillaris, Anthoxanthum odoratum, Arrhenatherum elatius, Dactylis glomerata, Festuca rubra, Holcus lanatus, Holcus mollis, Poa trivialis, Pteridium aquilinum, Dryopteris dilatata, Dryopteris filix-mas