Effectiveness of Dense Nesting Cover for Increasing Duck Production in Saskatchewan

We conducted a 3-year study (1992-94) in the parkland of southern Saskatchewan to evaluate effectiveness of dense nesting cover (DNC) as a means of increasing duck production in prairie-parkland nesting areas. Nest searches were conducted on 31 DNC plots and 31 unmanaged plots (UM). Mallard (Anas platyrhynchos), gadwall (A. strepera), northern shoveler (A. clypcata), and blue-winged teal (A discors) initiate<] 90% of the duck nests found. We restricted our analysis to nests of these 4 species (n = 997) to facilitate interspecific comparisons. Mean Mavfield nest success for the 4 duck species combined was greater (P = 0.038) in DNC (15%) than in UM (7% ) over the 3-year period. However, there was a significant species × treatment interaction (P = 0.038): mallard and gadwall had higher (P = 0.005) nest success in DNC (14-16%) than in UM (4%), whereas blue-winged teal and northern shoveler did not (10-15% in DNC vs. 10-14% in UM). Of the factors we examined year had the greatest effect on nest success (P = 0.002) For the 4 species combined. nest success varied among years from 8-26% in DNC and 4-16% in UM. Nest success also was highly variable among plots within years. Although the nest-success rate of mallards in 2 of 3 years exceeded the threshold (15%) considered necessary fo a stable population (16% in 1992, 24% in 1994), it was only 7% in 1993. Nest densities in DNC calculated from mean Mayfield nest-success rates and corrected for nest-search efficiency ranged from 1.1 to 1.4 nests/ha. Given the nest-success rates and densities observed, DNC would have to be established on a prohibitively large area to effect a substantial increase in regional duck production We recommend placement strategies for DNC plots and suggest increased conversion of cultivated land to pasture may be a more cost-effective strategy for increasing duck nunbers on the Canadian prairies.