To get to the estuary from the north, you drive along a broad dirt track. It seems unnecessarily wide, until you meet a tractor the size of a house trundling along it. The intensively cultivated fields eventually give way to pasture, grazed by the famous bulls used in bullfights. And at last, you reach the muddy creeks and channels of what is left of the estuary.

But the journey is worth the effort. This is the largest estuary in Western Europe, holding 54% of Portugal’s wintering waders, 30% of its wintering waterfowl, and 4% of its wintering herons. There are regularly over 50,000 birds in winter, and double that during the migration seasons.

About the Tagus Estuary Natural Reserve

Despite the 20,000ha of reclaimed land, the estuary upstream of Lisbon is still a vast intertidal zone of mudflats, bordered by 2,800 ha of saltmarsh (the largest in Portugal), saline marshlands, mudflats, shallow lagoons. Beyond this is a hinterland of dry grassland, cornfields, rice fields, stone pine and cork oak woodland. To the east some of this polder landscape has been somewhat modified by industrial and military installations which pose a serious threat of pollution, but the estuary is still frequented in winter and migration time by over 70,000 waders including 15% of western Europe’s wintering avocet, plus dunlin and curlew and several thousand duck.

Some 22,850 ha of the saltmarsh, mudflats and islands are included in a Reserva Natural, which was established in 1976 and covers an area of over 14,000 ha. Shooting and other forms of exploitation, except fishing, are forbidden. Access to the reserve for visitors is by road to perimeter then by footpath to points of interest, however, there is no entry to three strict nature reserves Reserva Integral areas that are left for nature to get on with its own business and even scientists are allowed in only to monitor the situation.

The protected area extends from 10m below sea level to 11m above, and is important for marine life such as fish, molluscs, crustaceans, etc, as well as birds.

Fortunately, the powers that be have recognised the value of the estuary:

• 1976 – creation of the Natural Reserve of the Tagus Estuary
• 1980 – declared a Wetland of International Importance by the Ramsar Convention
• 1994 – established as a Special Protection Area for Wild Birds, under EEC directive 79/409

Through the farmland

There were larks, finches and linnets in good-sized flocks, plenty of house sparrows and thousands of common starlings. Snowstorms of gulls followed tractors in the distance. Half a dozen little egrets flew out of a ditch as we approached and joined others in the fields together with lapwing, golden plover and godwit. Three cattle egrets stalked through another field, occasionally one stopped to stir up invertebrates with its foot, the way little egrets do in water. These birds have a peculiar rolling, goose like gait which distinguishes them from little egrets even at some distance.

A great grey shrike (below) hunted from the tops of weed stalks in a dry pasture, and a crested lark called.

Some of the birds

Avocet Recurvirostra avosetta

An elegant wader found in the intertidal areas and salt pans. It is most active at dawn and dusk, and also feeds by moonlight on insects and small crustaceans. It sweeps its up-curved bill through the water and mud, finding prey by touch. Seen mostly on migration and during winter, but also occasionally nests on the reserve. Wintering birds come from the Waddenzee area, and the Tejo estuary holds about 15% of the population that winters on the western European coast.

Black-Winged Stilt Himantopus himantopus

Found in saline lagoons and other wetlands, where its long legs enable it to feed in deeper water than other waders. It preys on floating or underwater animals such as tadpoles, water bugs, beetles and fly larvae. It is a common nesting species here, with some individuals staying over winter, however, most spend the winter in Africa.

Cattle Egret  Bubulcus ibis

Dunlin Calidris alpina

Found mainly in intertidal areas where it feeds on invertebrates on the mud near the mud surface as the tide recedes. At high tide it roosts in salt pans or marsh-side banks. Common passage migrant, and winter visitor with over 1% of the western European population in some winters.

Redshank Tringa totanus

Found in intertidal zones with thin sediments, salt pans and waterlogged agricultural land. Also known as the sentinel of the marshes, this species is always on the lookout for danger, and noisily proclaims it. Usually feeds in loose flocks. Common winter visitor, with about 2% of the European wintering population on the estuary. Also seen on migration, and has nested occasionally.

Wigeon Anas Penelope

Found in intertidal areas, in the shallow waters of the Estuary and in Saragoça salt pan. Flocks lift off almost vertically and land again as one. Feeds on vegetation, both submerged and on the surface. Common winter visitor with about 1% of the European population recorded here.

Shoveler Anas clypeata

It is very active at night, sifting the upper layers of water and mud for freshwater fleas, mosquito larvae, and other invertebrates through the beak. Common winter visitor, with about 2.3% of the European population recorded here.

Marsh Harrier Circus aeruginosus

Hunts over shallow, fresh or brackish waters, where there is emergent aquatic vegetation, and also over dense marshes. Spends the night on the ground or in marshes. Individuals spend the night in regularly-used roosts, which are located in marshes and reed beds. Nesting resident. Not common, but the reserve seems to support 40 to 50% of the national breeding population.

Black-tailed Godwit

The Giganta rice paddies , located about 4 km southwest of Porto Alto, extend for several kilometres and are an excellent place to see birds at all times of the year;  In autumn and winter, when the area is covered with stubble flooded, the land is frequented by flocks of lapwing and, snipe as well as the black-tailed godwits. Occasionally flocks of flamingos appear here too.

EVOA

Espaço de Visitação e Observação de Aves (Bird Observation and Visitation Space)

These days, there is a delight at the end of the long road. The Tagus Estuary Bird-watching and Conservation Area provides a facility to attract birds to lagoons and scrapes in front of a visitor centre and a series of hides. There are a shop, café, exhibition centre, classroom, guided tours, and other activities on site.

The site opened in 2012, after my last visit to the area. Most reviews of the place are good.  Experienced birdwatchers have told me the birds are wonderful, but the guided tours etc are a disappointment.  But, as with most places trying to attract customers, the tours etc are designed for the general public and for educational needs, so that needs to be borne in mind.

The EVOA website is being updated and expanded, but offers plenty of information about the tours etc. in Portuguese, English and French, and also a calendar of what birds you are likely to see in each month. Make sure you choose the language from the menu bar, or you get some very strange google translations of bird names.

Getting there

If have a car, access is from the N10, across the river from Vila Franco de Zira. EVOA is signposted. Some of the dirt roads are accessible if your vehicle has reasonably good ground clearance. Other areas are gated off, but you can buy a pass that allows access. There is more information about access and a map on the Portuguese Birdwatching site If you have a car, you can take your time, drive slowly and stop almost anywhere to look at birds. But don’t forget those huge tractors and whatever huge farm machinery they may be pulling.

If you are staying in Lisbon, you can get to Vila Franco de Zira by train, but will need a taxi from there. Probably the best way to see the area is by using a local bird-guide – several are listed on Birding Pals.

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