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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
Common Shelduck Tadorna tadorna	LC	passage (2001–2006)	14,480 birds	A4i, B1i, C3
Common Shelduck Tadorna tadorna	LC	winter (2001–2006)	3,064 birds	B1i, C3
Common Teal Anas crecca	LC	passage (2001–2006)	5,187 birds	B1i, C3
Common Ringed Plover Charadrius hiaticula	LC	passage (2001–2006)	690 birds	B1i, C3
Eurasian Curlew Numenius arquata	NT	passage (2001–2006)	2,180 birds	B2
Eurasian Curlew Numenius arquata	NT	winter (2001–2006)	1,535 birds	B2
Black-tailed Godwit Limosa limosa	NT	passage (2001–2006)	2,129 birds	B1i, C3
Dunlin Calidris alpina	NT	passage (2001–2006)	9,465 birds	B2
Dunlin Calidris alpina	NT	winter (2001–2006)	42,876 birds	A4i, B1i, B2, C3
Common Redshank Tringa totanus	LC	winter (2001–2006)	5,544 birds	A4i, B1i, C3
Common Redshank Tringa totanus	LC	winter (2001–2006)	4,359 birds	A4i, B1i, C3
A4iii Species group - waterbirds	n/a	passage (2001–2006)	45,896 birds	A4iii, C4
A4iii Species group - waterbirds	n/a	winter (2001–2006)	76,704 birds	A4iii, C4

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
Common Shelduck Tadorna tadorna	3,064 / 5,300 (birds)	58	poor
Northern Pintail Anas acuta	162 / 3,210 (birds)	6	very poor
Anas crecca	8,830 / 8,830 (birds)	100	good
Eurasian Golden Plover Pluvialis apricaria	1,560 / 2,650 (birds)	59	poor
Common Ringed Plover Charadrius hiaticula	690 / 205 (birds)	100	good
Eurasian Curlew Numenius arquata	1,535 / 1,230 (birds)	100	good
Eurasian Curlew Numenius arquata	2,180 / 1,340 (birds)	100	good
Dunlin Calidris alpina	42,876 / 46,600 (birds)	93	good
Dunlin Calidris alpina	9,465 / 7,800 (birds)	100	good
Common Redshank Tringa totanus	4,359 / 4,610 (birds)	95	good
Common Redshank Tringa totanus	5,544 / 4,350 (birds)	100	good
A4iii Species group - waterbirds	458,976 / 35,198 (birds)	100	good
A4iii Species group - waterbirds	76,704 / 102,890 (birds)	75	moderate

Pressure (threats to the trigger species and/or their habitats)
Threat	Timing	Scope	Severity	Result
No known threats	happe­ning now	few indivi­duals/small area (<10%)	no or slight decline (<1% over 3 gener­ations)	low

Response (conservation actions taken for the trigger species and/or their habitats)
Designation	Planning	Action	Result
Whole area (>90%) covered by appropriate conservation designation	Unknown	Not assessed	low

Year	Protected Area	Designation (management category)	% coverage of IBA
1985	Mersey Estuary	Site of Special Scientific Interest (UK) (IV)	100
1995	Mersey Estuary	Nature Reserve (IV)	20
2000	New Ferry	Site of Special Scientific Interest (UK) (IV)	1
2011	Mersey Estuary	Marine Protected Area (OSPAR) (UA)	73

Habitat	% of IBA	Habitat detail
Marine Intertidal	major (>10)
Marine Neritic	major (>10)
Marine Coastal/Supratidal	minor (<10)

Land use	% of IBA
nature conservation and research	-
urban/industrial/transport	-

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Mersey Estuary (United Kingdom). Downloaded from https://datazone.birdlife.org/site/factsheet/mersey-estuary-iba-united-kingdom on 23/12/2024.