Ecology and Management of Islands, Peninsulas and Structures for Nesting Waterfowl

Differential Use of Man-Made Islands for Nesting By Canada Geese

Robert L. Eng
Fish and Wildlife Program, Montana State University, Bozeman, MT 59717

Don A. Childress
Montana Department of Fish, Wildlife and Parks, Helena, MT 59620

Tom L. Carlsen
Montana Department of Fish, Wildlife and Parks, P.O. Box 998, Townsend, MT 59644

A population of 40-50 nesting pairs of Canada geese, seemingly limited from further increase by a lack of secure nesting sites, was exposed to 325 small, newly created islands in four nearby impoundments totaling 770 ha. Both dredged and haul islands were constructed and ranged in size from .0004 to 1.2 ha. The first new islands were available in 1974 with all available by 1978. Intensive nest searches conducted annually on old and new habit from 1973 through 1988 have provided data on numbers and distribution of nests, clutch sizes and nest success. A near-continuous increase in nesting pair use of the islands has been documented from 6 nests in 1974 to 320 in 1988. As colonization of the island habitat was initiated, geese appeared to select the larger islands. As densities of nesting geese increased, multiple nests on the larger islands occurred with increased but well-spaced use of smaller islands. The last sites selected appear to be the small, closely spaced islands.

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