Wetland Management

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Wetland Management

The motto for wildlife managers during the Dust Bowl era was to hold water for waterfowl use, as high as possible, for as long as possible, which in turn lead to developing wetland basins from depressions in the landscape to wetlands that were deeper. This motto for holding water high and long resulted in an immediate response by waterfowl. Birds took to the new habitat, only emphasizing the idea of more water.

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Holding water wasn't the only thing early managers did for waterfowl. Aquatic vegetation such as cattail and bulrush was encouraged to provide cover for duck nests and broods. Overwater nesters, such as, black-crowned night herons, Franklin's gulls, eared grebes, and white-faced ibis', have also taken advantage of the increasing vegetation growing in wetlands, making Refuge management not only for the ducks! Below the surface of the water, sago pond weed provides excellent food for water birds. Back in the early stages of the Refuge, managers would transplant this species to entice it to grow in other wetlands.

This old management philosophy of holding as much water as possible throughout the year was not always beneficial to wetlands and birds. Over the decades, managers have learned wetlands are dynamic, ever changing, and need periods of everything from dry years to flooded years. Wetland vegetation also changes based on water levels. For example, constant, high water levels lead to choked wetlands of both below water (submergent) and above water (emergent) vegetation.

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Today, managers also look at water quality, vegetation composition, weather, and bird use to determine management techniques needed to keep these wetlands productive. Some of the tools of the trade include drawing wetlands down completely or holding wetlands at different water levels each year. Vegetation control also includes draw-downs, because exposing sediments encourages new growth of plants, that provide food for various birds. We have learned floods can be a good thing. Natural flooding allows water to move into basins and back out as water recedes, thus freshening or “flushing” wetlands. Flooding can also help control unwanted vegetation by having water levels too high for certain plants to establish. Cattails in particular are a plant that needs monitoring and management, for they can take over and choke out a wetland. When a wetland is choked out by cattail, the ability for ducks to land, take off, or even swim is gone. Vegetation diversity, that supplies food for birds, is decreased, and the overall wetland productivity is diminished.

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Cattails can be controlled using draw-downs in conjunction with mowing, grazing, and/or discing, and herbicide treatments. Cattails can also be controlled by flooding if the water is higher than the young shoots.

Carp too can degrade a wetland's productivity and use by waterfowl. Carp are a non-native fish from Asia. When they feed, they stir up sediment, causing the water to become turbid. The turbidity decreases the ability for aquatic vegetation to grow due to lack of sunlight. The most effective way to control carp are to draw down a wetland completely, or allow for a winter kill.

During the field season, wetland managers on Hewitt Lake National Wildlife Refuge look at past, present, and future wetland management to determine what techniques are working and which are not. This helps managers develop an annual management plan so that quality habitat can be provided to a whole host of bird species year after year.