Changes in chemical characteristics of water in selected wetlands in the Cottonwood Lake area, North Dakota, U.S.A., 1967-1989
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North Dakota↗
Geology topics
George A. Swanson
Publications and source records attributed to George A. Swanson.
Foods and dietary strategies of prairie-nesting ruddy ducks and redheads
Actively feeding Ruddy Ducks ( Oxyura jamaicensis ) and Redheads ( Aythya americana ) were collected from North Dakota wetlands during the 1979-1981 breeding seasons. Foods found within esophagi were analyzed on a wet-weight aggregate percent basis. Male and prelaying and laying female Ruddy Ducks consumed >90% invertebrates, primarily chironomids. Postlaying female Ruddy Ducks consumed 73% invertebrates. Male and female (prelaying, laying, and postlaying) Redheads were consistently more omnivorous, consuming 51-70% invertebrates (mostly chironomids) and 30-49% plant matter. Seeds of shallow marsh emergent plants were important in the diet of prelaying and laying female Redheads in 1979, a wet year. Female Redheads used temporally available seed resources in shallow marshes to meet energy requirements for foraging on invertebrates in deeper, more permanent wetlands. Continued losses of easily drained shallow wetlands may represent a serious impediment to our efforts to maintain current Redhead population levels.
The Condor↗
Feeding Ecology of Breeding Blue-Winged Teals
A 5-year investigation of factors influencing the selection of foods consumed by blue-winged teals ( Anas discors ) during the breeding season in the glaciated prairie region of south-central North Dakota showed that birds first arriving on the breeding grounds consumed a diet consisting of 45 percent invertebrates. The proportion of animal foods in the diet increased to 95 percent at the onset of the nesting season. The quality and quantity of foods selected at any given time were influenced by the biological demands and morphological adaptations of the bird, the behavior and ecology of the invertebrates selected as foods, and the general nature of the aquatic ecosystems as determined by the hydrology and geology of the area and modified by land use and weather. Feeding activities changed significantly when food availability within the aquatic ecosystem changed. During the spring and early summer, temporary and seasonal wetlands, if not severely disturbed, were of paramount importance to breeding blue-winged teals since they provided abundant and readily available, high protein, animal foods. Later in the summer when seasonal wetlands began to dry up, insects began to emerge in the semipermanent ponds and lakes, and feeding intensity shifted to these more permanent waters. This trend, however, was often reversed temporarily during the early summer following heavy precipitation that refilled shallow water areas and again stimulated invertebrate development.
North Dakota↗
Selective predation by mink, Mustela vison, on waterfowl
Predation by mink ( Mustela vison ) on three types of ducks (captive, pen-reared-released and wild) was documented in two studies at the Northern Prairie Wildlife Research Center, Jamestown, North Dakota. In the first study, 36 of 60 flightless adult and juvenile ducks held on eight 0.1-acre experimental ponds disappeared between 10 July and 4 August 1969. Available evidence indicated that all were killed by a large adult mink. The mink selected recently released incubator-hatched ducklings, females in the process of incubating, and adults and juveniles on a marginal food supply.In the second study, 152 wood duck ducklings ( Aix sponsa ) were released on a 76-acre marsh during 1971. Half of the ducklings, when 24 to 27 days old, were placed at weekly intervals in four floating pens and allowed to escape after 4 days. Each time birds were placed in the floating pens, a comparable group was placed in a predator-proof shoreline pen. Birds in the shoreline pen escaped as they learned to fly when approximately 60 days old. The shoreline of the marsh was periodically searched, and the remains of 21 (28%) of the floating-pen birds were identified in food remains found at 16 mink dens. No remains of birds from the shoreline pen were found at the dens. Coots ( Fulica americana ) were also taken commonly. Wild ducklings appeared to have been almost totally consumed, but the legs and feet of the wood ducks were often left uneaten because of bands and tags.
American Midland Naturalist↗
Observation of nighttime feeding behavior of ducks
A night vision scope was used during 1969-71 to study the nighttime feeding behavior of ducks on prairie wetlands of south-central North Dakota. Adult and immature ducks were observed feeding between 9:00 PM and 4:00 AM, predominantly on midges (Chironomidae) and mayflies (Ephemeroptera). The emergence pattern of these insects appeared to be a major factor influencing duck activity and feeding behavior at night.
North Dakota↗