Browsing by Author "Livolsi, Mark C."
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Item Implications of uncertainty in true metabolizable energy estimates for estimating wintering waterfowl carrying capacities(Wildlife Society Bulletin, 2015-09-15) Livolsi, Mark C.; Ringelman, Kevin M.; Coluccy, John M.; Dibona, Matthew T.; Williams, Christopher K.Carrying capacity models for wintering waterfowl require estimates of energy availability based on food densities and true metabolizable energy (TME) of various food types. However, because TME values vary widely between studies, estimates of carrying capacity may be less precise than previously acknowledged. We explored how variation in TME values affected estimates of landscape-level energy availability for American black ducks (Anas rubripes), using 4 distinct approaches for assigning TME values to waterfowl food items collected over the winter period in 2011–2012 and 2012–2013: a “best practices” approach, which typically used average TMEs across species, a minimum and maximum reported values approaches, and a coarse-scale “order-average” approach. We found that all 4 approaches yielded significantly different estimates of energy availability across all saltmarsh habitat types. Additionally, we evaluated the potential management implications of variation in TME values by comparing energy supply on 1,223 ha of marsh in Prime Hook National Wildlife Refuge (DE, USA) using all 4 approaches for assigning TME values. We estimated carrying capacity and modeled depletion of energy on this refuge over a hypothetical wintering period. We found that even relatively small variations in TME values produced highly variable estimates of carrying capacity for the refuge. Thus, we recommend that researchers consider the inherent uncertainty in TME values of waterfowl foods, and explicitly include this variation in carrying capacity models. © 2015 The Wildlife Society.Item Subsampling Reduces Sorting Effort for Waterfowl Foods in Salt-Marsh Core Samples(Journal of Fish and Wildlife Management, 2014-07-23) Livolsi, Mark C.; Ringelman, Kevin M.; Williams, Christopher K.Waterfowl researchers often use soil core samples to estimate food availability in foraging habitats, and these estimates are needed for bioenergetic models of carrying capacity. However, core sampling is frequently a time- and resource-intensive process, and some researchers have suggested that subsampling may be a valuable way to reduce processing time. We evaluated whether 10% and 25% by mass subsampling are appropriate techniques for reducing core-sorting effort while maintaining precision for samples taken in six separate habitat types along the Delaware bayshore. We found no significant difference between biomass found in 100% sorted cores and estimated biomass obtained by 10% and 25% subsampling. We found that 10% subsampling offered the greatest time savings, reducing mean sorting times by 77% (from 13.7 hours to 3.3 hours) from 100% sorted cores. We recommend that researchers consider subsampling to reduce core-sorting effort and cost, particularly when processing large numbers of cores.