The Tagus Estuary holds the largest continuous wetland system on Portugal's Atlantic coast, a 14,563-hectare mosaic of mudflats, salt pans, and reed beds that claims 120,000 overwintering waterbirds each year. EVOA, the environmental interpretation centre anchored on the south bank near Vila Franca de Xira, opened in 2008 as the reserve's first permanent observation hub. Its wooden walkways extend 400 metres across reclaimed salt marsh, threading between shallow lagoons engineered to mirror the tidal rhythm of the estuary beyond. Lisbon birding tours depart from the centre's jetty and from municipal docks along the Lezíria Sul floodplain, following channels that bisect the mudflats at high tide. Black-tailed godwits, dunlins, and grey plovers crowd the exposed banks; avocets and black-winged stilts wade the shallows. Greater flamingos—a year-round population of roughly 2,000—filter brine shrimp in the salt pans, their presence a result of habitat restoration work that began in the late 1990s. Spoonbills, spoonbill colonies numbering 300 pairs, nest in tamarisk thickets on the reserve's eastern margin. Marsh harriers quarter the reeds. Short-eared owls hunt the levees at dusk. The reserve lies on the East Atlantic Flyway, a migratory corridor linking the Arctic breeding grounds with West African wintering sites. Spring passage peaks in April; autumn migration stretches from August through October. Rarities logged in recent years include red-necked phalaropes, Caspian terns, and glossy ibises. The estuary's productivity—nutrient upwelling from the Atlantic meeting freshwater discharge from the Tagus basin—fuels invertebrate blooms that sustain the flyway's energy demands. EVOA's observation hides face west across the main lagoon, positioned to use morning side light and avoid the afternoon glare that flattens plumage detail. Day passes grant access to the walkways, three fixed hides, and a floating blind tethered in the lagoon's centre. Guided boat tours circumnavigate the tidal islands, reaching zones closed to foot traffic. The reserve operates a citizen science program; sightings logged by visitors feed into the Portuguese rarity committee's annual report. October 2025 counts recorded 87 species in a single morning survey, a figure that reflects both the estuary's diversity and the intensity of migratory traffic during peak weeks.