Trappings of Success: Predator Removal for Duck Nest Survival in Alberta Parklands

Emily M Blythe,Mark S Boyce

doi:10.3390/d12030119

Abstract

Nest survival is most limited by nest predation, which often is increased by anthropogenic causes including habitat fragmentation, mesopredator release and predator subsidies. In mallards and other upland-nesting duck species in the North American prairies, the rate of nest survival is the vital rate most influential to population dynamics, with 15%–20% survival required for maintenance of stable populations. Predator removal during the nesting season has increased duck nest survival on township-sized (9324 ha) areas of agricultural ecosystems in eastern locations of the prairie pothole region (PPR). However, predator removal has not been evaluated in western parkland habitats of the PPR where three-dimensional structure of vegetation is considerably greater. During 2015–2017, we evaluated nest survival on control and predator-removal plots at two study areas in the parklands of central Alberta, Canada. In the second year of the study, we transposed predator removal to control for habitat effects. Estimates of 34-day nest survival did not significantly differ between trapped ( x ¯ = 20.9%, 95% CI = 13.2%–33.7%) and control ( x ¯ = 17.8%, 95% CI = 10.5%–30.0%) plots in any year. We do not recommend predator removal be continued in Alberta parklands due to its ineffectiveness at improving duck nest survival at the local scale.

Highlights

In mallards (Anas platyrhynchos) and presumably other duck species, nest survival is the most important vital rate influencing population dynamics in the Prairie Pothole Region (PPR) [1].Maintenance of stable dabbling duck (Anas spp.) populations requires ~15%–20% annual nest survival [2,3,4]; success defined as the hatching of at least one duckling
In all but one study area-year combination, we found no significant difference in nest survival between control and predator removal plots (Table 2)
The majority of research evaluating predator removal to increase dabbling duck nest survival has found it to be effective when applied in prairie habitats [19,23,24,25,26,27]; but publication bias towards significant results might have influenced the prevalence of positive findings [29]

Summary

Introduction

In mallards (Anas platyrhynchos) and presumably other duck species, nest survival is the most important vital rate influencing population dynamics in the Prairie Pothole Region (PPR) [1].Maintenance of stable dabbling duck (Anas spp.) populations requires ~15%–20% annual nest survival [2,3,4]; success defined as the hatching of at least one duckling. In mallards (Anas platyrhynchos) and presumably other duck species, nest survival is the most important vital rate influencing population dynamics in the Prairie Pothole Region (PPR) [1]. Anthropogenic habitat alteration has led to increased nest predation [4,5,7]. Nest predation is the strongest limiting factor of nest survival in ducks [8], and most bird species [9]. Mesopredator release, resulting from the loss of regulatory influence by apex predators, can contribute to enhanced richness and abundance of mid-trophic level predators [10,11]. Concentration of nests in limited habitat, ease of travel by predators and loss of landscape heterogeneity can enhance foraging efficiency of avian and mammalian predators [7,14,15,16]. A rich guild of nest predators, arising from anthropogenic changes to the environment, will have a diversity of foraging behaviours that increases the risk to all nests regardless of nest distribution strategy [17,18]

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Results

Discussion

Conclusion