An Evaluation of Seasonal Predator Removal on Duck Nest Success
on Waterfowl Production Areas in Minnesota and North Dakota
ALAN B. SARGEANT AND MARSHA A. SOVADA
U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research
Center,
Route 1, Box 96C, Jamestown, ND 58401
A 5-year evaluation of effects of seasonal predator removal on duck nest success on Waterfowl Production Areas (WPAs) was initiated by Northern Prairie Wildlife Research Center in 1987. This study, supported by several federal, state, and private entities, is being conducted on WPAs in western Minnesota and eastern North Dakota in cooperation with local wetland management districts. Data were obtained for 11 pairs of treatment/control study area-years during 1986-89; study areas ranged in size from 156 to 747 acres.
The predator removal is conducted annually from about late March to early July in a manner that mimics or is part of operational management programs. Principal target species are red fox, striped skunk, raccoon, badger, and Franklin's ground squirrel. No avian predator removal is conducted but few avian nest-predators are present. Predator occurrence on treatment and control areas is monitored by track searches and observations. Three duck nest searches are conducted annually of each treatment and control WPA. Nests are checked at about 7 to 10-day intervals and fate recorded.
The removal is conducted by experienced trappers using leg-hold traps (mostly
soft-catch), 110 and 220 connibears, live traps, snares, and shooting. A total
of 347 adult mid-size carnivores were removed from these areas (
=31.5
per area, range=6 to 59 per area). These were striped skunk (57%), raccoon
(26%), red fox (12%), badger (4%), and mink (I %). Other predators removed
were 33 juveniles of above species, 9 weasels, and 41 Franklin's ground squirrels.
Predator survey data indicate that nearly all predator species active on each
area at the beginning of the nesting season were present at the end of the
season.
Nest success data were available for 10 pairs of treatment/control study
area-years. Nest success (Mayfield corrected) on treatment areas ranged from
2 to 50% (=17.2%) and
on control areas from 2 to 63% (
= 17.2 %). Numbers of nests found ranged from 7 to 192 on treatment areas
and from 7 to 49 on control areas. Predation accounted for 91 and 94% of nest
failures on treatment and control areas, respectively. Data for 1990 will
be discussed.
Proper interpretation of data must await completion of the study but several conclusions are apparent: (1) high variability in nest success among small areas should be expected and must be taken into account in developing evaluation strategies, (2) exclusion of predator species from small areas is difficult to achieve using available techniques, (3) numbers of predators removed is not a valid gauge of effectiveness of predator removal programs, (4) predator removal is an art requiring considerable attention that is most effective when conducted by highly experienced trappers having a variety of methods available for use.
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