The scarlet ibis — Eudocimus ruber — flies up to sixty kilometers each day to feed in the coastal mudflats of Piauí, then returns en masse to mangrove roosts on Ilha Grande at sunset, a daily migration that has shaped the ecology of the Parnaíba Delta for millennia. The spectacle, known locally as the revoada, sees flocks numbering in the thousands converge between 17:30 and 18:30, their crimson plumage igniting against the fading light. Portuguese colonists first documented the phenomenon in the eighteenth century, mistaking the birds for flamingos. Indigenous Tremembé communities had long revered the ibis as a seasonal marker, timing fishing expeditions to the birds' return. The Parnaíba Delta, the only oceanic delta in the Americas, spans 2,700 square kilometers across seventy-three islands, its labyrinthine channels and tidal mangroves creating one of the continent's most biodiverse estuaries. The scarlet ibis nests here from March through September, feeding on crustaceans whose carotenoid pigments sustain the species' signature red coloration. By the 1980s, habitat loss and unregulated tourism had reduced nesting colonies by nearly forty percent. A 10-real conservation fee, introduced in 2018 and collected at Porto dos Tatus, now funds mangrove restoration and seasonal access restrictions. Visitors over twelve pay the levy, which has generated more than 1.2 million reais since implementation. The passeio revoada dos guarás parnaíba departs from Porto dos Tatus on Ilha Grande between 14:00 and 19:00 daily, with most operators recommending arrival by 15:00 to allow ninety minutes of navigation through the delta's interior canals before reaching the primary roosting site. The journey crosses the Rio Igaraçu, threading past submerged carnaúba palms and crab-harvesting villages. Tour durations range from two to four hours depending on vessel type; speedboat safaris complete the route in under two hours, while traditional motorized canoes extend the experience to sunset and beyond. The ibis return regardless of weather, their arrival triggered by circadian rhythm rather than light alone, meaning overcast evenings yield equally dense flocks. Conservation protocols prohibit vessels from approaching closer than fifty meters to the nesting trees, a rule enforced by environmental monitors stationed on the water during peak season. The birds tolerate observation at this distance, spiraling into the canopy in waves. Populations peak in May and June, when juveniles join the evening return. By October, most ibis migrate north to breeding grounds along the Maranhão coast, leaving the mangroves to resident herons and roseate spoonbills until the following March.