wetlands ecology

by Bryan Dixon

Types of wetlands in the Cutler Marsh
Benefits of wetlands to humans

More information on wetlands & wetlands organizations

More information on wetlands flora & fauna

Types of wetlands in Cutler Marsh

  • Riverine Systems
  • Riparian Zones
  • Upland Fields and Wet Meadows
  • Playa Wetlands
  • Emergent Wetlands
  • Open Water

    Riverine Systems (streams) carry more oxygen than still waters and their gravelly stream bottoms provide hiding places for small invertebrates. The smaller invertebrates become food for larger invertebrates such as caddisfly larvae. Fish look for these spots as a replenishing food source. Birds, such as Belted Kingfishers and Forster's Terns, dive into the water to take fish. Other birds, such as Great Blue Herons and egrets, wade in the shallows for their fish. Snowy Egrets have even evolved with yellow toes, which they dangle ahead of them as bait, waiting for fish to take the nibble - only for the fish to become a nibble themselves!

    Riparian Zones (along stream banks) provide a unique boundary habitat (ecotone) where animals can take advantage of both wet and dry habitats. Banks just above water level are used for nest sites by geese and ducks. Once hatched, the young have only a short distance to go to reach the safety of water. Look for writhing masses of garter snakes on south-facing banks in the spring; they're taking advantage of the warm sun on cool days. Muskrat and beaver will leave the water to feed on the shoots and bark of shrubs and trees, but they build their huts among the reeds and rushes and even hollow out tunnels in the banks, where they can be safe from roaming canines. Deer, elk, and even moose have been observed in the Wetlands Maze Area feeding on the willow shoots or hiding in the dense cover of summer growth. The structural diversity of the riparian shrubs and trees provides a mix of food and cover, and wherever there's a diverse plant community, we find a diverse animal community.

    Shrubs and trees also provide safe nesting places for Yellow Warblers, Warbling Vireos, Willow Flycatchers, Eastern Kingbirds, Common Yellowthroats, and Bullock's Orioles. Great Blue Herons build colonies of nests in trees. In early spring you may even see Great Horned Owls - or perhaps a Canada Goose - usurping these high platforms for their own nests. Once evening insects are plentiful a variety of bats roost in the trees, though they're harder to find because they’re nocturnal.

    Upland Fields and Wet Meadows beyond the riparian zone along the edge of the Maze may look dry for much of the year, but part of the year these lands often have standing water. Plant species in these wetlands must be specially adapted for seasonal fluctuations. Spring rains and warmer temperatures result in new green shoots growing up through last year's brown stubble, and animals take advantage of the bounty. Chorus frogs blend their raucous voices on spring evenings. Sandhill Cranes arrive to feed on young plant shoots and insects. Meadow voles, mice and pocket gophers lace the ground with burrow entrances and runways, but they'd better watch out, because coyotes, fox and other mammals may be waiting patiently at the ends of these "rodent roads." In the air, Northern Harriers and Short-eared Owls fly low, listening for scratching sounds, and their broad wings and long tails give them superb maneuverability to turn and dive suddenly for a bit of fast food.

    One of the first signs of spring is the Killdeer's familiar "ka-DE ka-DE". These small shorebirds with a black double neck-band scratch out a nest in the stones but the eggs are almost impossible to find. On summer's evenings, look for White-faced Ibis flying low - dark, slender shorebirds with downward curving bills flying in tight formation, heading home to their rookery north of the Valley View Highway.

    Another important habitat in these upland wetlands is the buffer zone along the edges of fields where farmers leave higher grasses. These tall grasses look "weedy and unkempt" but provide cover for Ring-necked Pheasants and Savannah Sparrows.

    Playa Wetlands (alkali mud flats) look desolate along the edges of the Wetlands Maze; it seems they're just sticky mud after spring rains, or crunchy crisp in mid-summer. But although sparsely vegetated, there are plants here such as salt tolerant pickle weed and knot weed, though few animals can eat them. The real bounty lies beneath the surface in the form of invertebrates and crustaceans. Different species of these tiny animals live at different depths below the surface, and shorebirds have evolved with different bill shapes to take advantage of this diversity. Watch American Avocets sweeping the surface of shallow waters for swimming insects but notice how the Black-necked Stilts (the ones wearing a "tuxedo" plumage) probe the mud. Long-billed Dowitchers can be recognized from a distance by their sewing-machine-like feeding. Look for Willets, perhaps the most common shorebird, with their relatively thick bills and black-and-white striped wing patterns that are displayed whenever they land. In early spring, and again in late summer, look for appropriately named Greater Yellow-legs, with large and slightly up-curved bills, and the Lesser Yellowlegs with proportionately smaller bills. All of these shorebirds depend on shallowly submerged or exposed mudflats for their dinner.

    Emergent Wetlands are the most prominent form of wetlands in Cutler Marsh. Here the water is shallow enough that plants can anchor their roots in the bottom silts and yet reach upward above the surface for air and sunlight. The two most common plants are cattails and hardstem bulrush. Where the water is shallow, a variety of birds use these plant communities for cover, nesting and food. These birds are very difficult to see, but you can hear their voice as dusk settles in early summer. Listen for the haunting "pump-pump-a-LUNK" of the American Bittern. The Sora makes a sound like its name, "so-RAH so-RAH". The Virginia Rail utters a repeated "ka-DICK ka-DICK".

    In the upper reaches of the cattails you may find other birds. Marsh Wrens are the tiny chattering birds that always seem to keep their tails pointed upward. Look at them through binoculars to notice the beautiful brown and black colors on their backs. Common Yellowthroats are another bird that you may find easier by voice. This small warbler has a distinctive song, "WITCHity-WITCHity-WITCHity", but also a beautiful yellow breast with a striking black mask.

    Open Water is another important habitat in the Wetlands Maze. Technically, "open water" means water too deep for emergent plants to root. Safe from land-based predators, here we find the swimming birds of the marsh. Some of these birds rely on the plants for food, some dive for fish. In spring, you'll see waves of different species beginning with ducks such as Northern Pintails, Redheads, and Green-winged Teal. Early in March, look for the regular flock of 50-70 Tundra Swans. By late March and early April, you'll see American Pelicans with their bizarre "nose knobs" that disappear in summer. Also by summer we find Double-crested Cormorants, Western and Clark's Grebes. And ever-present are the American Coots, which, although similar to ducks, actually belong to the family of Gallinules. These birds are specially adapted for diving, with flaps on their toes that only stick out when being pushed back in strong swimming motions.

    More information on wetlands & wetlands organizations

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