Creating and managing wetland impoundments to provide habitat for aquatic birds
Patuxent Research Refuge, located in Central Maryland (USA), has approximately 140 ha of impoundments that were constructed for recreational and wildlife conservation purposes. Impoundments are of three major designs: dammed ravines, excavated basins, and diked ponds. Over 50 species of wetland plants were transplanted to impoundments of Patuxent from many parts of the United States between 1945 and 1963 to determine the species best suited for establishment in tannin-stained infertile waters. The wood duck was the only waterfowl species commonly observed on the Refuge when the area was established, but Canada geese, mallards, and black ducks, were introduced and numerous techniques developed to improve nesting and brood habitat. Twenty-six waterfowl species and 80 species of other water birds have used the impoundments for resting, feeding, or nesting. Management is now conducted to optimize avian biodiversity. Management techniques include drawdowns of water every 3-5 years in most impoundments to provide maximum plant and invertebrate food resources for wildlife. Research on the impounded wetlands at Patuxent has included evaluation of vegetation in regard to water level management, improving nest box design to reduce use of boxes by starlings, imprinting of waterfowl to elevated nesting structures to reduce predation on nests, and drawdown techniques to increase macroinvertebrates. Data on waterfowl abundance are evaluated relative to management activities and a preliminary computer model for management of the impoundments has been developed. Past, present, and future management and research projects are reviewed in this paper.