Energetic Carrying Capacity of Submersed Aquatic Vegetation in Semi-Permanent Wetlands Important to Waterfowl in the Upper Midwest

Gross, Margaret C.; Lancaster, Joseph D.; Simpson, John; Shirkey, Brendan T.; McClain, Sarah E.; Jacques, Christopher N.; Davis, J. Brian; Hagy, Heath M.

doi:10.1007/s13157-019-01208-0

Cited by 4 publications

(15 citation statements)

References 30 publications

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“…Using arguable, yet still conservative threshold for biological significance of 50% for submersed aquatic vegetation, our methods (ratio = 38%) would fail to meet the criteria. Moreover, the mean difference in TME N values between our collection methods (0.39 kcal/g) was small (14.4%) relative to the range of previously reported estimates for submersed aquatic vegetation (range = 2.73 kcal/g; Stuckenia pectinata −1.07 kcal/g, Elodea canadensis —1.66 kcal/g; Gross ) and of all estimates reported in the literature across waterfowl species (range = 5.1 kcal/g; S. pectinata −1.07 kcal/g, Cyperus esculentus —4.03 kcal/g; Petrie et al ). Typical application of TME values in energetic carrying capacity models relies on aggregations of food items by wetland or land cover type for large‐scale conservation planning exercises (e.g., Soulliere et al ).…”

Section: Discussioncontrasting

confidence: 48%

“…Although inherently large variability in processing efficiency of aquatic vegetation among individual mallards contributed to our inability to claim practical equivalency between collection methods, the means and ranges of TME N values reported herein resemble those of other species of aquatic vegetation (McClain , Gross ). In their comparison among methods of estimating endogenous energy losses during TME trials, Sherfy et al () postulated a priori that a mean difference in TME between individuals relative to the mean TME for the 2 methods exceeding 20% warranted biological significance.…”

Section: Discussionmentioning

confidence: 67%

“…Unexpectedly high levels of variation (CV = 107–133%) among samples within both methods indicated that our power to detect a difference was likely low and led to equivocal results. Recent assessments of TME N of aquatic vegetation have similarly noted high variation among individual ducks (McClain , Gross ) relative to previous studies that have evaluated mainly seeds and grains (Checkett et al , Kaminski et al , Ballard et al , Dugger et al , Coluccy et al ). Before adopting the harness method as a standard in TME N assay, researchers should fully evaluate differences or equivalency in TME N excreta collection methods using additional widgeongrass samples or an alternative food source with demonstrated low variation, such as moist‐soil seeds or tubers, using appropriate sample sizes.…”

Section: Discussionmentioning

confidence: 89%

“…Only when both one‐sided tests were rejected ( P ≤ 0.05) did we consider the observed effect close enough to zero to be practically equivalent (Lakens ). For each observed effect, we chose equivalency bounds calculated as 10% of the range from 139 TME N assays of 10 submersed aquatic diet items for wild mallards (Table ; Gross ). We did not explicitly measure the amount of processing time required at each step of the process for each sample independently, but we estimated the average or range of times required to complete each component of the TME assays postprocessing.…”

Section: Methodsmentioning

confidence: 99%

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Assessment of excreta collection methods to estimate true metabolizable energy of waterfowl foods in wild ducks

Lancaster¹,

McClain²,

Gross³

et al. 2019

Wildl. Soc. Bull.

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True metabolizable energy (TME) of waterfowl foods is commonly estimated for use in energetic carrying capacity models in association with conservation planning efforts under the North American Waterfowl Management Plan. Researchers define and estimate TME as the net energy from excreta collected from an individual after feeding a precise quantity of a food item compared with excreta collected during a fasted control. We evaluated an alternative excreta collection method for use in TME assays for comparison with traditional excreta collection methodology for waterfowl. We fed widgeongrass (Ruppia maritima) to wild‐caught mallards (Anas platyrhynchos) during autumn 2016 at Forbes Biological Station, Havana, Illinois, USA, and quantitatively collected excreta using a harness‐style excreta collection method and a traditional basin‐style collection method. We were unable to find support for a difference in total excreta energy, mass loss, and TME estimates between collection methods, but high variation in TME among samples prohibited our ability to consider the collection methods similar. Time required for processing harness samples was 60–175 minutes less per sample than for basin samples. The basin method has been the standard for TME trials on waterfowl, but we found the harness method to be much more efficient and potentially allow for better animal husbandry practices. We suggest the harness method be tested further with increased sample sizes or alternate foods prior to widespread application, but researchers conducting TME assays of waterfowl foods should consider using this method in the future. © 2019 The Wildlife Society.

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Section: Discussioncontrasting

confidence: 48%

Section: Discussionmentioning

confidence: 67%

Section: Discussionmentioning

confidence: 89%

Section: Methodsmentioning

confidence: 99%

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Assessment of excreta collection methods to estimate true metabolizable energy of waterfowl foods in wild ducks

Lancaster¹,

McClain²,

Gross³

et al. 2019

Wildl. Soc. Bull.

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“…Specifically, gadwall have larger gizzards and intestinal ceca than mallards, which may increase the birds' processing efficiency and energy assimilation from vegetation (Barnes and Thomas 1987, Hunt et al 2019). Despite considerable variation in gut morphology among North American Anatidae (Barnes and Thomas 1987) and apparent plasticity within species (Miller 1975), if incorporating multi‐species estimates have minimal effect on achieving habitat conservation objectives, a single species estimate may be robust (Livolsi et al 2015, Gross et al 2019).…”

mentioning

confidence: 99%

Variation in True Metabolizable Energy Among Aquatic Vegetation and Ducks

et al. 2020

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Avian diet quality is typically measured using true metabolizable energy (TME N ), which is a measure of assimilable energy of food items accounting for innate endogenous losses. Originally developed for use in the poultry industry, TME N methods have been adapted to determine the value of natural foods consumed by waterfowl to parameterize bioenergetics models for conservation planning. Because there is little knowledge of the variation in TME N estimates among food items and waterfowl species, we investigated TME N of 6 common species of submersed aquatic vegetation for mallards (Anas platyrhynchos; i.e., a diet generalist) and gadwall (Mareca strepera; i.e., a diet specialist) in the midwestern United States during autumn 2015-2017. We precision fed and collected excreta from ducks using standard bioassays to estimate TME N . Mallards had slightly greater TME N than gadwall, but there was considerable variation in TME N among vegetation species, duck species, and individuals within each species. True metabolizable energy (±SE; kcal/g[dry]) for mallards was greatest for Canadian waterweed (Elodea canadensis; 1.66 ± 0.26), followed by coontail (Ceratophyllum demersum; 1.51 ± 0.28), southern naiad (Najas guadalupensis; 1.37 ± 0.39), sago pondweed (Stuckenia pectinata; 0.50 ± 0.22), wild celery (Vallisneria americana; 0.05 ± 0.42), and Eurasian watermilfoil (Myriophyllum spicatum; -0.13 ± 0.42). Mean TME N for gadwall was greatest for Eurasian watermilfoil (0.77 ± 0.32), followed by Canadian waterweed (0.70 ± 0.31), coontail (0.55 ± 0.28), southern naiad (-0.61 ± 0.34), wild celery (-0.98 ± 0.39), and sago pondweed (-1.07 ± 0.33). Generally, TME N for most vegetation species was less than agricultural grains, but it was similar to ranges reported for seeds of naturally occurring hydrophytic vegetation and aquatic macroinvertebrates. We recommend that conservation planners incorporate species-specific TME N estimates in bioenergetics models and that future researchers improve TME N assays for wild waterfowl following our recommendations.

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Factors Affecting Wetland Use by Spring Migrating Ducks in the Southern Prairie Pothole Region

2021

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There is increasing recognition of the importance of wetlands in the prairie pothole region (PPR) of the northern United States for stopover habitat for spring-migrating waterfowl. The quality and quantity of stopover habitat found near breeding areas can affect speed and success of migration and subsequent breeding events. Conservation and management of wetlands in the region has traditionally focused narrowly on reproductive phases of the life cycle, and little to no research has examined how ducks use a diversity of available wetlands in the region during migration. We conducted weekly surveys on 1,061 wetlands during spring 2018 and 2019 to examine factors affecting duck use of wetlands in the intensively modified southern PPR landscape of Iowa, USA, for wetland restoration and conservation strategies. We compared wetland types, which included farmed, seasonal, and semi-permanent wetlands, and lakes. The highest duck use per unit area occurred on semi-permanent wetlands, followed by seasonal, and then farmed wetlands, and lakes. Ducks were highly clustered in our study, with 75% of all use-days occurring on only 37 wetlands comprising 41% of all wetland area surveyed. We used hurdle models to examine how local and landscape factors measured within and around wetlands influenced duck use during spring migration. Multiple factors related to duck use at local and landscape scales, such as wetland area, vegetation abundance, and number of wetlands in the surrounding landscape. Among semi-permanent wetlands, local factors within wetlands were more important than landscape factors in determining duck use. Collectively, our findings suggest semi-permanent wetlands within the PPR play a key role in transitioning birds from wintering areas to breeding areas and that management of semi-permanent wetlands should promote interspersion of emergent vegetation and open water and growth of submersed aquatic plants to improve their function for migrants.

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Energetic Carrying Capacity of Submersed Aquatic Vegetation in Semi-Permanent Wetlands Important to Waterfowl in the Upper Midwest

Cited by 4 publications

References 30 publications

Assessment of excreta collection methods to estimate true metabolizable energy of waterfowl foods in wild ducks

Assessment of excreta collection methods to estimate true metabolizable energy of waterfowl foods in wild ducks

Variation in True Metabolizable Energy Among Aquatic Vegetation and Ducks

Factors Affecting Wetland Use by Spring Migrating Ducks in the Southern Prairie Pothole Region

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