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Evans, D.J. and M.J. Evans. 1986. Territory parameters in snowy owls wintering in the Duluth-Superior harbor. Final report submitted to the Nongame Wildlife Program, Minnesota Department of Natural Resources. Unpaged.
The Duluth-Superior harbor is a traditional wintering area for Snowy Owls (Nyctea scandiaca). High prey densities, resulting from grain spillage from trains, trucks, and around grain elevators, have supported the highest reported densities of wintering Snowy Owls in North America. Winter counts, conducted since 1973, have varied from lows of 10-15 owls to as high as 60 or more, presumably in response to arctic and subarctic microtine cycles.
The Nongame Wildlife Program of the Minnesota Department of Natural Resources contracted with D. Evans to further investigate, via radiotelemetry, territory parameters of Snowy Owls wintering in the urban-industrial environment of the Duluth-Superior harbor.