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Nesting Ring-necked Ducks in Minnesota: Success and Failure

ROBERT T. EBERHARDT AND MARK L. SPERRY

Minnesota Department of Natural Resources, 102 23rd Street,
Bemidji, MN 56601

As part of an investigation into age-related productivity of ring-necked ducks (Aythya collaris), nest fate was determined from a sample of 188 nests found in typical unmanaged habitat of north-central Minnesota. The study area consisted of five bog lakes ranging in size from 11 to 145 ha in the vicinity of Bemidji, Minnesota. Nest searching was conducted each June from 1978 through 1985. Nesting habitat was searched by 2- to 5-person crews on foot or by canoe using flushing poles. Approximately 80 ha of habitat was searched each year. The fate of each nest was determined and nest success rates were calculated using the modified Mayfield method. Cause of nest failure was recorded, and in cases of predation an effort was made to identify the nest predator. Ring-necked duck nest success ranged from 10 to 74% ( GIF -- mean symbol

= 25%). Predation was the primary cause of nest failure, accounting for 89.6% of all nest losses. Nest abandonment and flooding accounted for 8.3% and 2.1%, respectively. Of the destroyed nests where a predator was identified, 85.7% were attributed to mammalian predators. Mink (Mustela vison) were responsible for 44.9%, raccoon (Procyon lotor) for 14.3%, and unidentified mammalian predators thought to be either mink, raccoon, or river otter (Lutra canadensis) accounted for 24.5% of all depredated nests. The only avian predator was the American crow (Corvus brachyrhynchos); it was implicated in 14.3% of all nest failures.

Most avian predation occurred early in the nesting cycle and was often compensated by persistent renesting. Mammalian predation, which occurred later, could be a limiting factor in some years to population growth.

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