DETERMINATION OF POPULATION TRENDS AND FACTORS RELATED
TO THOSE TRENDS OF FISHPOINT REFUGE MALLARDS


Lee Gosson
Sehool of Science and Natural Resources
Lake Superior State University
Sault Ste. Marie, MI 49783

April 15, 1997


ABSTRACT:	To study population trends of mallards (Anas platyrhynchos) banded at Fishpoint
Wildlife Refuge from 1970-1995, analysis of the ratios of youug to adults, and females to males
were done. It was found that for the ratio young to adults, the mean was 2.5 young per every 1
adult. For the ratios of females to males, the mean was 1 2. A runs test was done to determine if
the trends for these ratios were cyclic. At 95%, it was found that the ratios of young to adults did
tend to be cyclic. Studies by Johnson 1994, and Arnold et al. reported similar results, and suggested
that droughts in the  nesting areas were responsible. Conditions at Fishpoint did not vary significantly
in water level or habitat, therefore other factors could have heen responsible. For the ratios of
females to males, the runs test ssuggested that the data was not cyclic. Differences in the ratios yf
frmales to males was most likely due to changes in hunting pressure and harvest ratios of females
to males.
	Relative vulnerability, which is the likelihood of one cohort being harvested compared to that
of another cohort, was also exanimed. Young males were compared to adult males, young females,
and adult females. It was found that young males were 1.1 time more vulnerable than adult males,
1.4 times more vulnerable than young females, and 1.6 times more vulnerable than adult females.
Factors that were responsiblefor these values are previous exposure to hunting, and bag limits which
favor the harvest of males over fr)~)jale5 Thcsc i~esuits agreed ~~~ith trends reported hy the USFWS.
~'e,~all, the trends yf the Fish/)oint 1?7all(l1~ds are sinular 10 those reported Jor other mallard
populations. H~'ever, the reasons %oi soi,ic 0 the ti~ends may vary, and analysis of individual
populations should determine the/actors th(il relate which directly influence (hat population.


SELIœCTED REFERENCES:

Brownie C., D. Anderson, K. Burnharn, and D. Robson. 1985. Statistical inference from band
recovery data: a handbook. Second ed. U.S. Fish & Wildlife Service. Resource Publication.
156. 305 pp.

Heitmeyer, M. L. Fredrickson~ and D. Hurnburg. 1 993 . Further evidence of biases associated with
hunter-killed mallards. Journal of Wildlife Managemen~. 57:105-113.

Smith, G., and R. Reynolds. 1 992. Huntin(~ an d mallard survival, 1979-88. Journal of ~ildlife
Management. 55:306-316.