Dense nesting cover (DNC) has been a conspicuous component of habitat management for upland‐nesting ducks for >30 years, but its benefits for nesting ducks have been contentious. During 1994–1999 we monitored 3,058 dabbling duck (Anas spp.) nests in 84 DNC fields located throughout the Canadian Parklands to examine sources of among‐field variation in nest density and nesting success. Nest density averaged 1.51 (SE=0.15) nests/ha and overall nesting success was 20.4%, but there was pronounced annual variation in both estimates. Nesting success increased with increasing field size (range = 6–111 ha), but nest density remained constant. Nest density increased with percent wetland habitat within DNC fields and declined with percent perennial cover in the surrounding 2.4 × 2.4‐km landscape, but these variables were not important for predicting nesting success. Nest abundance and nesting success roughly doubled in fields seeded with alfalfa (Medicago sativa) or sweet clovers (Melilotus spp.), but there was no benefit from using native as opposed to tame grasses. We recommend that waterfowl managers in the Canadian Parklands establish DNC with alfalfa in large fields in landscapes with abundant wetlands but minimal competing cover.
Early hatched waterfowl are more likely to enter the breeding population. Managers' primary tool to increase nesting success in the Prairie Pothole Region (PPR) of North America is managing upland vegetation for duck nesting cover. To determine whether managed covertypes affect early‐season nesting success, we modeled seasonal variation in nesting success using >17,000 duck nests found in managed and unmanaged covertypes in prairie Canada from 1993 to 2000. Nesting success was higher in most managed covertypes than in unmanaged covertypes early in the nesting season. Planted cover appeared to be the best managed covertype for increasing early‐season nesting success as it had high early‐season nesting success, and was selected by nesting ducks in greater proportion than its availability; however, nesting success in planted cover declined later in the nesting season while nesting success in most unmanaged covertypes increased. Nevertheless, even with reduced nesting success late in the season, planted cover was more productive than surrounding unmanaged covertypes. Future waterfowl management efforts should focus on providing safe nesting cover early in the nesting season.
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