Comparison of Food Quantities and Cover Density
on St. Clair Flats State Game Area

Vickie J. Schafer
School of Science and Natural Resources
Lake Superior State University


Abstract Waterfowl brood surveys are a new type of management tool used by the Michigan
Department of Natural Resources to measure nesting success. They are performed from May
until the first of July each year on predetermined survey routes. The St. Clair Flats State Game
Area was split into two survey routes, the east and west sides. A significant difference (p<O.OO1)
occurred in the number of broods recorded on the east and west sides over seven study years.
Food quantity and cover density were believed to be the possible limiting factors in the nesting
success on the west side. Five samples in each of twelve random locations were taken on each
side on May 4-5 while the females were nesting or incubating and on June 1-2 when the ducklings
were searching for food on their own. Macroinvertebrate samples consisted of O.5 liters of
substrate and plant material taken from under the standing water of the ditches. Cover density
was sampled using a cover pole marked with 16 decimeters. A multi-response permutation
procedure was used to test macroinvertebrate density between locations within each area, and
these were compared to the other area. No significant differences occurred between the two
areas or the two seasons (spring--p<O.38; summer-p<O.23; east--p<O.26; west--p<O.32). A
t-test was used to test cover density for each season, and it also showed no difference (spring--
p<O. I 8; summer--p<O. 1 6). Since a difference occurred between the two areas in brood
production, a characteristic not studied here appears to be the limiting factor in nesting success on
the west side of the game area.


Selected References

Drobney, R. D., and L. H. Fredrickson. 1979. Food selection by wood ducks in relation to
breeding status. Journal of Wildlife Management 43:109- 119.

Swanson, 0. A., M. I. Mavis, and V. A. Adomaitis. 1985. Foods consumed by breeding mallards
on wetlands of South-central North Dakota. Journal of Wildlife Management 49:197-
203.