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Location Portugal, Alentejo
Central coordinates 8o 43.00' West  38o 27.00' North
IBA criteria A4i, A4iii, B1i, B2, C2, C3, C4, C6
Area 24,633 ha
Altitude 0 - 30m
Year of IBA assessment 2002

Sociedade Portuguesa para o Estudo das Aves

Site description A large estuary with extensive mudflats and saltmarshes, located in central Portugal, c.50 km south of Lisbon. Setúbal is the main town in its vicinity. The inner part of the estuary is bordered by rice-fields and reedbeds, whereas the north-western limits are densely populated and the south-western parts are sheltered from the open sea by a sandbar.

Key Biodiversity Several waterbird species (mainly waders) occur in winter in large, internationally significant numbers, and the site holds 20,000 or more wintering waterbirds on a regular basis. There are also important numbers of breeding waterbirds, notably Himantopus himantopus and Sterna albifrons. The rice-fields are an important feeding ground for the egrets and herons from the nearby breeding colony at Murta dam (024). More than 500,000 Columba palumbus roost within the IBA in winter.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
White Stork Ciconia ciconia resident  1996  50-70 breeding pairs  good  C6  Least Concern 
Ixobrychus minutus breeding  1996  common  C6  Not Recognised 
Purple Heron Ardea purpurea breeding  2002  15 breeding pairs  good  B2, C6  Least Concern 
Egretta garzetta non-breeding  1996  common  C6  Not Recognised 
Great Cormorant Phalacrocorax carbo winter  1996  1,000-2,200 individuals  good  B1i, C3  Least Concern 
Western Marsh-harrier Circus aeruginosus resident  1996  5-6 breeding pairs  medium  C6  Least Concern 
Himantopus himantopus breeding  1996  200-800 breeding pairs  good  A4i, B1i, C2, C6  Not Recognised 
Pied Avocet Recurvirostra avosetta winter  1996  2,000-4,000 individuals  good  A4i, B1i, B2, C2  Least Concern 
Black-tailed Godwit Limosa limosa winter  1996  2,000-11,000 individuals  good  B1i, C3  Near Threatened 
Dunlin Calidris alpina winter  1996  12,000-16,000 individuals  good  B1i, B2, C3  Least Concern 
Collared Pratincole Glareola pratincola breeding  1996  5-20 breeding pairs  medium  C6  Least Concern 
Little Tern Sternula albifrons breeding  1996  50-100 breeding pairs  good  B2, C6  Least Concern 
A4iii Species group - waterbirds winter  1996  20,000 individuals  unknown  A4iii, C4   

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Estuário do Sado Nature Reserve 23,971 protected area overlaps with site 20,011  
Estuário do Sado Wetlands of International Importance (Ramsar) 25,588 protected area overlaps with site 24,633  


IUCN habitat Habitat detail Extent (% of site)
Forest Broadleaved evergreen woodland; Mixed woodland  -
Shrubland Sclerophyllous scrub, garrigue and maquis  -
Wetlands (inland) Standing freshwater; Water fringe vegetation  -
Artificial - terrestrial Arable land; Forestry plantations; Other urban and industrial areas  -
Coastline Lagoons; Mud flats & sand flats; Salt marshes; Sand dunes & beaches; Tidal rivers & enclosed tidal waters  -

Land use

Land-use Extent (% of site)
agriculture -
fisheries/aquaculture -
forestry -
hunting -
nature conservation and research -
tourism/recreation -
urban/industrial/transport -

Protection status National Partial International High20,011 ha of IBA covered by Nature Reserve (Estuário do Sado, 23,971 ha). 24,633 ha of IBA covered by Special Protection Area (Estuário do Sado, 24,633 ha). IBA also overlaps with Ramsar Site (Estuário do Sado, 25,588 ha).

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Sado estuary. Downloaded from on 22/10/2016

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