[/quote][QUOTE=Steel3's]I was reading the latest Wildlife Society Bulletin which included a paper by Jason H. Caswell and F. Dale Caswell titled "Vulnerability of mallards to hunting with a spinning-wing decoy in Manitoba" (volume 32(4), pages 1297-1304). Here are some of the highlights:
1) They conducted 72 experimental MARSH hunts between 8 Sept. and 11 Nov. 2001. A MARSH hunt consisted of 24 Herter's magnum mallard decoys, natural vegetation for concealment, a Mojo spinner, and hunters were encouraged to use calls as they saw fit. The spinner was turned "on" for 15 minutes, then "off" for 15 minutes with a 3-minute buffer in between. Whether it was "on" or "off" first was alternated each hunt.
They conducted 27 experimental MARSH hunts and 55 experimental FIELD hunts between 8 Sept. and 30 Oct. in 2002. MARSH hunts were the same as 2001. FIELD hunts consisted of 24 super-magnum Carry-lite Canada goose decoys and 24 magnum mallard decoys using Cabela's Goose Chairs as well as natural vegetation for concealment. Spinner and call use was the same as for MARSH hunts.
2) Hunts ranged from 1.0 to 3.0 hours with the average being 1.4 hours.
3) For experimental MARSH hunts, mallards were 1.9 times more likely to fly within gun range, the number killed/hour/hunter was 5.0 times greater, and the crippling rate was 1.7 times lower when the spinner was "on" compared to when it was "off".
4) For experimental FIELD hunts, mallards were 6.4 times more likely to fly within gun range, and the number killed/hour/hunter was 33 times greater when the spinner was "on" compared to when it was "off".
Crippling rate on experimental FIELD hunts was not different early in the season (before Oct. 5th), but was 3.7 times lower in the late season when the spinner was "on" compared to when it was "off".
Crippling rates (cripples lost per bird hit) averaged:
MARSH: 17.3% with spinner "on", 29.1% with spinner "off"
FIELD: Early season - 13.3% with spinner "on", 12.5% with spinner "off"
..........Late season - 9.2% with spinner "on", 34.4% with spinner "off"
5) There was no difference in the age ratio (juveniles/adults) or sex ratio (males/females) in the MARSH or FIELD hunts due to the spinner being "on" or "off".
6) The body-condition index (a metric of the bird's mass adjusted for it's skeletal size) was greater for mallards killed with the spinner "on" compared to when it was "off".
The discussion focussed mainly on the crippling rate and body condition data because their increased hunting success was fairly similar to information collected in CA, IL, MO, and MN. In the "Management Implications" section they summarized the considerations in regulating spinners and concluded with this point ...... and I'll quote:
Given the differential kill rates found in this study, we believe that prolific SWD use in Manitoba, Prairie Canada, or throughout Canada will not alone be reason to justify altering harvest regulations. However, harvest is only one component of many biological and political factors involved in regulation-setting process in Canada. A decline in hunter numbers from the 1974-79 average to the 1997-2001 average by approximately 63, 66, and 59% was accompanied by concurrent declines in mallard harvests by 45, 67, and 60% in Manitoba, Prairie Canada, and Canda respectively. Additionally, mallard harvest in Canda between the same periods declined from 25 to 11% of North American harvest. Before making a prediction of the impact of SWD's on harvest at local, regional, and national scales, we need to determine the number of hunters already using a SWD and the proportion of harvest that they represent.
I don't give a damned what the study says, they need to be banned. For making predictions at local, regional and national scales why not extrapolate?
