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The site was identified as internationally important for bird conservation in 2007 because it was regularly supporting significant populations of the species listed below, meeting ('triggering') IBA criteria.

Populations meeting IBA criteria ('trigger species') at the site:

Species	Red List	Season (year/s of estimate)	Size	IBA criteria
European Storm-petrel Hydrobates pelagicus	LC	breeding (2006)	1,398 pairs	B2, C2, C6
European Shag Gulosus aristotelis	LC	breeding (2006)	1,296 pairs	A4i, B1i, B3, C3
Ruddy Turnstone Arenaria interpres	NT	winter (1984–1985)	940 birds	A4i, B1i, C3
Lesser Black-backed Gull Larus fuscus	LC	breeding (2006)	3,335 pairs	A4i, B1i, B3, C3
Great Black-backed Gull Larus marinus	LC	breeding (2006)	901 pairs	B3
Common Tern Sterna hirundo	LC	breeding (1999)	96 pairs	C6
Common Tern Sterna hirundo	LC	breeding (2006)	78 pairs	C6

Ideally the conservation status of the IBA will have been checked regularly since the site was first identified in 2007. The most recent assessment (2007) is shown below.

State (condition of the trigger species' populations)
Species	Actual vs Reference (units)	% remaining	Result
European Storm-petrel Hydrobates pelagicus	1,398 / 2,130 (pairs)	66	poor
European Shag Gulosus aristotelis	1,296 / 1,200 (pairs)	100	good
Lesser Black-backed Gull Larus fuscus	3,335 / 3,760 (pairs)	89	moderate
Great Black-backed Gull Larus marinus	901 / 1,000 (pairs)	91	good
Roseate Tern Sterna dougallii	0 / 5 (pairs)	0	very poor
Common Tern Sterna hirundo	78 / 105 (pairs)	75	moderate

Pressure (threats to the trigger species and/or their habitats)
Threat	Timing	Scope	Severity	Result
Invasive and other problematic species and genes	happe­ning now	most of popul­ation/area (50–90%)	moderate decline (10–30% over 3 gener­ations)	high
Human intrusions and disturbance	happe­ning now	some of popul­ation/area (10–49%)	slow decline (1–10% over 3 gener­ations)	medium

Response (conservation actions taken for the trigger species and/or their habitats)
Designation	Planning	Action	Result
Whole area (>90%) covered by appropriate conservation designation	A management plan exists, but it is out of date or not compre­hensive	Substantive conservation measures are being implemented, but these are not compre­hensive and are limited by resources and capacity	medium

Year	Protected Area	Designation (management category)	% coverage of IBA
1974	Isles of Scilly	Heritage Coast (V)	100
1976	Isles of Scilly	Area of Outstanding Natural Beauty (V)	100
1986	Castle Down (Tresco)	Site of Special Scientific Interest (UK) (IV)	10
1986	Gugh	Site of Special Scientific Interest (UK) (IV)	7
1986	Samson (With Green, White, Puffin & Stony Islands)	Site of Special Scientific Interest (UK) (IV)	7
1986	Shipman Head & Shipman Down (Bryher)	Site of Special Scientific Interest (UK) (IV)	7
1986	Chapel Down (St, Martin'S)	Site of Special Scientific Interest (UK) (IV)	6
1986	Wingletang Down (St, Agnes)	Site of Special Scientific Interest (UK) (IV)	3
1986	Eastern Isles	Site of Special Scientific Interest (UK) (IV)	6
1986	St, Helen's (With Northwethel & Men-A-Vaur)	Site of Special Scientific Interest (UK) (IV)	3
1986	Annet	Site of Special Scientific Interest (UK) (IV)	3
1986	Great Pool (Tresco)	Site of Special Scientific Interest (UK) (IV)	2
1986	Plains & Great Bay (St, Martin'S)	Site of Special Scientific Interest (UK) (IV)	2
1986	Tean	Site of Special Scientific Interest (UK) (IV)	2
1986	Lower Moors (St, Mary'S)	Site of Special Scientific Interest (UK) (IV)	1
1986	Rushy Bay & Heathy Hill (Bryher)	Site of Special Scientific Interest (UK) (IV)	1
1986	Big Pool & Browarth Point(St, Agnes)	Site of Special Scientific Interest (UK) (IV)	1
1986	Norrard Rocks	Site of Special Scientific Interest (UK) (IV)	1
1986	Pool Of Bryher & Popplestone Bank (Bryher)	Site of Special Scientific Interest (UK) (IV)	1
1986	Western Rocks	Site of Special Scientific Interest (UK) (IV)	<1
1987	Higher Moors & Porth Hellick Pool (St, Mary'S)	Site of Special Scientific Interest (UK) (IV)	2
1989	Peninnis Head (St, Mary'S)	Site of Special Scientific Interest (UK) (IV)	2
1989	White Island (Off St, Martin'S)	Site of Special Scientific Interest (UK) (IV)	2
1989	Porth Seal (St, Martin'S)	Site of Special Scientific Interest (UK) (IV)	<1
1995	Pentle Bay, Merrick and Round Islands	Site of Special Scientific Interest (UK) (IV)	8
1996	St, Martin's Sedimentary Shore	Site of Special Scientific Interest (UK) (IV)	6
1996	Watermill Cove	Site of Special Scientific Interest (UK) (IV)	-
1996	Porthloo	Site of Special Scientific Interest (UK) (IV)	<1
2005	Isles of Scilly Complex	Marine Protected Area (OSPAR) (UA)	16
2014	Isles of Scilly	Marine Protected Area (OSPAR) (UA)	11

Habitat	% of IBA	Habitat detail
Marine Coastal/Supratidal	major (>10)
Marine Intertidal	major (>10)
Marine Neritic	major (>10)
Grassland	minor (<10)	Mesophile grasslands
Shrubland	minor (<10)	Heathland
Wetlands (inland)	minor (<10)	Standing freshwater

Land use	% of IBA
tourism/recreation	-

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Isles of Scilly (United Kingdom). Downloaded from https://datazone.birdlife.org/site/factsheet/isles-of-scilly-iba-united-kingdom on 23/12/2024.