Impact of management treatments on waterfowl use of dense nesting cover in the Canadian parklands

Abstract

Periodic treatment of established stands of dense nesting cover (DNC) is a recommended practice to maintain cover quality, but little information exists on the magnitude and duration of treatment effects on nesting waterfowl. During 1998-2001, we examined the effect of management treatments on vegetative characteristics and waterfowl nest success and density in fields of DNC seeded to introduced and native grass and forb mixes in the parklands of Saskatchewan and Manitoba. We measured vegetation height-density and litter depth within fields and located and monitored 1,927 duck nests within 33-42 fields/yr ranging in size from 6 ha to 62 ha. We considered a series of models examining the influence of grass type and management treatment (GTMT) and years post-management (YPM) on vegetative characteristics, nest success, and nest density while including covariates potentially affecting these response variables. Visual obstruction and litter depth were lowest in native-burned fields and greatest in introducedhayed fields. Visual obstruction was low the year following management, peaked 2-3 YPM, and remained at intermediate levels through !6 YPM. Litter depth remained low for the first 3 YPM and increased thereafter. Nest success and nest density varied little among GTMT. Nest success was high (14.3%) the year following a management treatment, low (6.5%) at 2 YPM, and moderate thereafter. Nest success decreased with percent cropland in the surrounding landscape. Nest density was 0.7 nests/ha the first year following management, increased to approximately 1.3 nests/ha in years 2-3, and declined back to approximately 0.7 nests/ha for !6 YPM. Nest density decreased with field size and increased with the area of small wetlands, percent cropland, and percent wetland within surrounding landscapes. Nest density tracked vegetation density as expected and our results indicate a possible trade-off between nest density and nest success. Given ancillary data on small mammal and insect prey in our study fields, and evidence from other studies, we speculate that DNC fields may act as prey reservoirs during years of peak vegetative density with a consequent reduction in nest survival. Therefore, management to increase waterfowl production based on our results needs to consider the interaction of treatment effects, competing habitats, and surrounding landscape composition. ß 2011 The Wildlife Society.

Effects of Grassland Biomass Harvest on Nesting Pheasants and Ducks

“…Modeling nest density as the number of nests per plot required measuring predictors at the plot scale, and the most important predictors were related to vegetation height in the plot and habitat surrounding the plot, with both vegetation height and the area of wetlands within 500 m of each plot center being positively correlated with nest density. Typically, mallard and blue-winged teal densities are greater in habitats with greater wetland densities (Johnson and Grier, 1988), and our study supports previous findings that nest density is positively correlated to the proximity of wetlands (Arnold et al, 2007;Devries and Armstrong, 2011). Biomass harvesting equipment is vulnerable to damage and not efficient when operated near wetlands and on wet ground when used to harvest biomass in late autumn (Williams et al, 2012).…”

“…Although more data are required to determine how much refuge is necessary to optimize the joint production of waterfowl and bioenergy, we recommend orienting refuges closer to wetlands to support nesting waterfowl. Similar studies are needed to record nest survivorship and density for two or more years following biomass harvest (Devries and Armstrong, 2011) and to expand the spatial scale beyond 8 ha plots.…”

“…Biomass yields from WMAs in southwest Minnesota were about 3 Mg ha 21 (Jungers et al, 2013), which could bring revenues for achieving expansion goals. Moreover, biomass harvest could be used as an alternative to more resource-intensive prescribed burning to maintain early-successional plant communities (Devries and Armstrong, 2011). If resulting habitat characteristics and wildlife benefits are similar for both management operations, biomass harvest could provide funds through sales of biomass and also conserve funds by reducing costs of prescribed burning.…”

“…For instance spring grazing and prescribed burning decreased the density of blue-winged teal (Anas discors) nests in North Dakota but did not influence nest success (Kruse and Bowen, 1996). Positive effects of biomass removal were evident when waterfowl nest success and density increased after mowing and burning of restored grasslands in Canadian prairies (Devries and Armstrong, 2011). The mechanisms underlying the varying effects of other biomass removal techniques on nest success and distribution are related to both local and landscape characteristics.…”

Duck Productivity in Restored Species-Rich Native and Species-Poor Non-Native Plantings

“…This heterogeneity likely created more suitable habitats for alternative prey, especially small mammals [73,77,78]. If native plantings supported more alternative prey, nest predators may have responded resulting in a more dramatic increase in predation of nests relative to DNC as generalist predators became more abundant [79-83]. Alternatively, characteristics of native vegetation might be preferred relative to DNC for nest predators, thus, a response of alternative prey may not be needed as an intermediary and native vegetation might directly attract a greater density of nest predators regardless of abundance of alternative prey.…”