Waterfowl Use of Dense Nesting Cover in the Canadian Parklands

Abstract

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.

Effects of Grassland Biomass Harvest on Nesting Pheasants and Ducks

“…To account for nests that failed before discovery, we used a Horvitz-Thompson estimator of total nests initiated per plot based on model-estimated DSR and average nest age at discovery (Arnold et al, 2007):…”

“…Although plots were similar in size (mean 7.9 ha 6 0.4 SD), we included plot area as an offset variable to control for subtle variation in plot size. These habitat covariates have been used to describe variation in nest density and survival in previous studies (Reynolds et al, 2001;Stephens et al, 2005;Arnold et al, 2007;Kruse and Bowen, 1996). Models were compared and ranked based on AIC c .…”

“…The mechanisms underlying the varying effects of other biomass removal techniques on nest success and distribution are related to both local and landscape characteristics. Increases in nest success have been associated with nest-scale habitat variables such as vegetation height (Luttschwager et al, 1994), field-scale variables such as legume cover (Arnold et al, 2007), and landscape-scale variables such as surrounding grassland cover (Stephens et al, 2005;Thompson et al, 2012) and fragmentation (Horn et al, 2005). Therefore, analysis at multiple spatial scales is important for understanding the effects of management activities on reproductive rates (Koper and Schmiegelow, 2006).…”

Social and habitat correlates of immigrant recruitment of yearling female Mallards to breeding locations

“…These females have an estimated C90% probability of belonging to the yearling (i.e., first breeding season) age class based on physical characteristics of GSC feathers (Krapu et al 1979). Marked females were located by radio-telemetry 2 or 3 times daily and monitored throughout the breeding season to determine survival and reproductive fate relative to broad-scale habitat enhancement programs delivered across the aspen parklands (Devries et al 2003;Emery et al 2005;Arnold et al 2007). Radio-marked females that disappeared from the study area prior to nesting were believed to be transients and were censored from analyses.…”

“…In the analysis, the capture of a yearling female recruit was considered a Bernoulli trial and whether a recruit was an immigrant or natal PARKLAND resident was a binomial event (e.g., Hazler 2004;Arnold et al 2007). This approach allowed information about variability of the number of trials and events among study areas to be incorporated into the analysis.…”