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Effects of a Legal Drain Clean-Out on Wetlands and
Waterbirds: A Recent Case History

Methods


Precipitation Patterns and Water Regimes

I obtained annual precipitation records for 1892-1994 from measurements taken at local gaging stations in order to relate precipitation in western Sargent County to water depths in BBMK. For 1892-1931, precipitation data were from Forman, North Dakota, and for 1932-1994, precipitation measurements were averaged for the Oakes, Verona, Lisbon, and Forman gaging stations to the west, northwest, north, and east of BBM.

Water-depth information for BBMK before and after the Drain No. 11 clean-out came from measurements made during visits to the wetlands during 1962-94 in conjunction with studies at BBMK (Krapu and Duebbert 1974, U.S. Water and Power Resources Service 1980). Additional information on the presence and extent of surface inundation of BBMK was available from aerial and ground photographs taken between 1937 and 1994 by the U.S. Department of Agriculture, the U.S. Fish and Wildlife Service, the U.S. Bureau of Reclamation and others.

Emergent Vegetation/Open Area Measurements

Open water areas (to the nearest 0.1 ha) were determined for BBMK from digitized maps prepared from vertical aerial photographs taken in July 1990. Open water areas within BBMK were compared to similar measurements made in 1979 prior to the Drain No. 11 clean-out by biologists of the U.S. Water and Power Resources Service. I compared percent change in open water area at BBM from 1979 to 1990 with Kraft Slough located several kilometers from Drain No. 11 (Figure 1).

Measurement of Wetland Habitat and Water Conditions

Total basin areas by wetland class for all Sargent County wetlands were obtained from digitized maps prepared by the U.S. Fish and Wildlife Service National Wetland Inventory; classification is based on basin water regime (Cowardin et al. 1979). The total area of each wetland habitat type (temporary, seasonal, semipermanent, and lake) in Sargent County was measured to determine the proportion of wetland habitat in the County affected by the Drain No. 11 clean-out. The status of wetland habitat in Sargent County before the Drain No. 11 clean-out is based on conditions existing in May 1979 when aerial photography was taken for the National Wetland Inventory.

Comparison of Waterbird Use Among Wetlands

Waterbird usage of BBMK before the Drain No. 11 clean-out was estimated from surveys made in late spring and summer of 1979. These surveys documented species diversity and density at BBMK. Kraft Slough, recognized for its diverse and abundant waterbird community (Kantrud 1973, Krapu and Duebbert 1974), served as a control for assessing whether Drain No. 11 (prior to clean-out) affected waterbird use of BBM. Densities of breeding waterbirds are from single counts on each wetland made during 27 May-6 June 1979. Counts were made by 2 biologists who recorded by species all adult waterbirds visible on each wetland with the aid of spotting scopes and binoculars. Counts were made from land and over water using canoes. After the number of individuals of each species had been tallied, the density of each species was determined for each wetland. Species use of BBMK by density was next ranked, and a one-way ANOVA performed on these ranks. Ties in density ranks between wetlands were treated as described in Conover (1980) under rank transformation. Density ranks of sora (Porzana carolina Linnaeus) and Virginia rails (Rallus limicola Vieillot) were not included in the analyses because methods used were not reliable for measuring densities of these highly secretive species. Number of active nests of waterfowl and colonial-nesting waterbirds, and adults with dependent young of all species of waterbirds were also recorded. Prior to 1986, I had visited Bruns, Big, and Kraft sloughs during most years dating back to the mid-1950s to observe waterfowl and other waterbirds. During 1986-90, I visited BBMK each spring, summer, and fall and recorded status of water conditions and surveyed the wetlands for waterfowl and other waterbirds. Information gained from my spring and fall visits, existing literature, and interviews with retired local game wardens comprised information used to address spring and fall use of BBM by migratory waterfowl before and after clean-out of Drain No. 11.

Dispersal Characteristics of Sargent County Waterfowl

To gain a better understanding of where ducks and geese that stage or are reared in Sargent County disperse and provide recreation, I obtained and summarized waterfowl band recovery records for waterfowl banded in Sargent County, North Dakota during 1951-89. Band recoveries were separated into locally-reared birds (immatures flightless when banded) and birds capable of flight. The data were obtained from the Office of Migratory Bird Management at Laurel, Maryland and included recovery locations for 690 ducks and 751 geese banded by the U.S. Fish and Wildlife Service.


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