Northern Prairie Wildlife Research Center
Ecology and Management of Islands, Peninsulas and Structures for Nesting
Waterfowl Production on Rock Islands and Floating Nesting Structures in
Brett K. Calverley and Gary R. Stewart
Ducks Unlimited Canada
Edmonton, Alberta, Canada T5S 1K9
Waterfowl use and success of rock islands and floating nesting structures in Alberta
were investigated during 1984, 1985 and 1988. Nesting use by Canada geese (Branta
canadensis) on both types of structures exceeded that of ducks with the exception
of floating structures in the forest biome. Nesting use by Canada geese on rock
islands averaged 74, 66 and 61 percent in the parkland, dryland prairie and irrigated
prairie respectively. Corresponding nest success values were 88, 100 and 92 percent.
Duck nesting use averaged 1 to 6 percent on rock islands in the three areas with
success ranging from 86 percent in the parkland to 100 percent in the two prairie
areas. Overall, the nesting use (and percent success) for Canada geese and ducks
combined was 67 (94) and 3 (88) percent respectively. Total waterfowl nests per
rock island were 0.80, 0.67 and 0.62 for parkland, dryland prairie and irrigated
prairie respectively. Percent nesting use by Canada geese and ducks on floating
nesting structures was 57 and 14 in the parklands; 17 and 21 in the forest and
36 and 18 overall. Corresponding values for percent success were 92 and 67 in
the parkland, 75 and 80 in the forest and 88 and 75 percent overall. The incidence
of more than one nest per structure was slightly higher for floating nesting structures.
Total waterfowl nests per structure was 0.71, 0.39 and 0.55 in the parkland forest
and overall respectively.
No correlation was found between used and unused structures. The key to success
was basic-abundant nesting material, sufficient freeboard and structures surrounded
by water. Additional data is required to determine if nesting use on floating
nest structures will increase with time. Both rock islands and floating nesting
structures are effective and secure nest sites for waterfowl in Alberta.
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