Found along the fringes of estuaries, tidal marshes flood and drain as the tides roll in and then creep back out. These wetlands range from fresh to salty, and they act as buffer zones between land and water. Tidal marshes in North America span from northern Maine to Texas along the eastern coastline. They support a host of species from tiny crustaceans to large birds such as the great egret. With so much life, it's not unusual to see foxes, river otters, birds and other predators in a tidal marsh.

Making a Marsh
Tidal marshes form when sediment starts building up along the edge of an estuary. Here, plants can grow without being tossed by waves and currents. Once grasses and other plants take root, they trap more sediment and stabilize the coastline. As estuary waters rise and fall with the tides, more sediment is left behind and the wetland soon grows.

Marsh and Landings
Brimming with life, tidal marshes support a surprising array of species, including some that rely on these habitats as stopovers along migration routes.

Not only do many plants collect sediment to expand a marsh area, they also trap nutrients consumed by tiny floating plankton-which jump-start the wetlands food chain. Much like an open estuary, the species of a tidal marsh stick to the spots that suit them best. Benthos, or bottom-dwelling creatures, forage along the floor for waste products.

Marshes provide welcome feasts along migration routes for long-distance travelers. Spain's Doñana National Park is a vital fueling station for European birds, such as the greylag goose (Anser anser), that cross the Sahara to winter in tropical Africa.