IBA Criteria

Year of most recent IBA criteria assessment: 2007

Populations of IBA trigger species
Species Current IUCN Red List Category Season Year(s) of estimate Population estimate IBA Criteria Triggered
Northern Gannet Morus bassanus LC breeding 2004 32,094 breeding pairs A4ii, B1ii, B2, C3
A4iii Species group - seabirds n/a breeding 1999-2001 31,611 breeding pairs A4iii, C4

Note: This table presents the IBA criteria triggered and the species that triggered then at the time of assessment, the current IUCN Red List category may vary from that which was in place at that time.

For more information about the IBA assessment process and criteria please click here

IBA Monitoring

Most recent IBA monitoring assessment
Year of assessment Threat score (pressure) Condition score (state) Action score (response)
2007 high favourable high
Was the whole site covered? Yes State assessed by Population
Accuracy of information good

Threats to the site (pressure)
Threat Level 1 Threat Level 2 Timing Scope Severity Result
Biological resource use fishing & harvesting aquatic resources - unintentional effects: large scale happening now whole area/population (>90%) slow but significant deterioration high
Climate change and severe weather habitat shifting and alteration likely in long term (beyond 4 years) majority/most of area/population (50-90%) moderate to rapid deterioration medium

Condition of key/trigger populations (state)
Scientific Common TargetPop ActualPop Units Remaining Result
Morus bassanus Northern Gannet 33000 32094 breeding pairs 98 favourable
Species group - seabirds A4iii 33510 31611 breeding pairs 95 favourable

Conservation actions taken at site (response)
Conservation Designation Management Planning Conservation Action Result
Whole area of site (>90%) covered by appropriate conservation designation A comprehensive and appropriate management plan exists that aims to maintain or improve the populations of qualifying bird species Substantive conservation measures are being implemented but these are not comprehensive and are limited by resources and capacity high
For more information about IBA monitoring please click here

IBA Protection

Protected Area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)
West Wales Marine / Gorllewin Cymru Forol Site of Community Importance (Habitats Directive) 737,614 protected area contains site 0
Pembrokeshire Marine/ Sir Benfro Forol Site of Community Importance (Habitats Directive) 138,038 protected area overlaps with site 11
Pembrokeshire Marine / Sir Benfro Forol Marine Protected Area (OSPAR) 0 protected area overlaps with site 0
Pembrokeshire Coast National Park 61,476 protected area overlaps with site 11
Grassholm/Ynys Gwales Site of Special Scientific Interest (UK) 12 protected area overlaps with site 9
Grassholm Island National Nature Reserve 11 protected area overlaps with site 11
Grassholm Marine Protected Area (OSPAR) 1,700 protected area overlaps with site 0
Grassholm Nature Reserve 8 protected area overlaps with site 0
Grassholm Special Protection Area (Birds Directive) 1,774 protected area contains site 11
Grassholm RSPB Reserve 11 is identical to site 11


IUCN Habitat Habitat detail Extent (% of site)
Grassland -
Coastline Sea cliffs and rocky shores, Rock stacks and islets -
Marine Coastal/Supratidal -
For further information about the habitat classification please click here.

Land use

Land-use Extent (% of site)
nature conservation and research -
tourism/recreation -
For further information about the land use classification please click here.

Recommended citation
BirdLife International (2023) Important Bird Areas factsheet: Grassholm. Downloaded from on 20/03/2023.