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

Ryan D Haffele,Cami S Dixon,Michael W Eichholz,Brock Fenton

doi:10.1371/journal.pone.0068603

Ryan D Haffele, Cami S Dixon + Show 2 more

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https://doi.org/10.1371/journal.pone.0068603

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Abstract

Conservation efforts to increase duck production have led the United States Fish and Wildlife Service to restore grasslands with multi-species (3-5) mixtures of introduced cool season vegetation often termed dense nesting cover (DNC). The effectiveness of DNC to increase duck production has been variable, and maintenance of the cover type is expensive. In an effort to decrease the financial and ecological costs (increased carbon emissions from plowing and reseeding) of maintaining DNC and provide a long-term, resilient cover that will support a diversity of grassland fauna, restoration of multi-species (16-32) plantings of native plants has been explored. We investigated the vegetation characteristics, nesting density and nest survival between the 2 aforementioned cover types in the Prairie Pothole Region of North Dakota, USA from 2010–2011 to see if restored-native plantings provide similar benefits to nesting hens as DNC. We searched 14 fields (7 DNC, 271 ha; and 7 restored native, 230 ha) locating 3384 nests (1215 in restored-native vegetation and 2169 in DNC) in 2010-2011. Nest survival was similar between cover types in 2010, while DNC had greater survival than native plantings in 2011. Densities of nests adjusted for detection probability were not different between cover types in either year. We found no structural difference in vegetation between cover types in 2010; however, a difference was detected during the late sampling period in 2011 with DNC having deeper litter and taller vegetation. Our results indicate restored-native plantings are able to support similar nesting density as DNC; however, nest survival is more stable between years in DNC. It appears the annual variation in security between cover types goes undetected by hens as hens selected cover types at similar levels both years.

Highlights

Declines in numerous populations of grassland nesting birds are thought to be caused by declines in productivity due to loss of native grasslands [1,2,3,4,5,6,7]
Studies indicated the mixture of intermediate wheatgrass (Thinopyrum intermedium), tall wheatgrass (Thinopyrum ponticum), alfalfa (Medicago sativa), and sweet clovers (Melilotus spp.) commonly referred to as dense nesting cover (DNC) is more productive for duck production than the 3-5 species of native vegetation that were established for comparison when grasslands were initially restored [13,14]
In the early sampling period, there was no difference (F1,5= 0.03, p = 0.87) in height between the cover types, as native plantings had an average height of 8.94 ± 0.85 cm and DNC plantings had a height of 10.22 ± 1.61 cm

Summary

Introduction

Declines in numerous populations of grassland nesting birds are thought to be caused by declines in productivity due to loss of native grasslands [1,2,3,4,5,6,7]. The Prairie Pothole Region of North America is an important nesting region for grassland nesting birds, as wetland densities on the breeding grounds produce abundant food sources attracting breeding birds [10] This area has undergone extensive modification due to agricultural development including a loss of >70% of its native grasslands [11,12]. DNC is typically associated with a cyclic management regime, as it reaches maximum growth in the first 2–4 years after planting, often loses its structural quality the 4-5 years as it is outcompeted by species of vegetation that are undesirable to nesting birds. DNC appears to achieve the primary purpose of providing quality duck habitat, it does not create a self-supporting ecosystem resilient to perturbation without further assistance; a goal of true restoration [34,35]

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