Ken Reinecke and Rick Kaminski, LMVJV Waterfowl Working Group. Final revision of Table 5 (Duck energy-days; DEDs)

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1 1 MEMORANDUM FROM: SUBJECT: TO: Ken Reinecke and Rick Kaminski, LMVJV Waterfowl Working Group Final revision of Table 5 (Duck energy-days; DEDs) Rich Johnson and Tom Edwards Leaders, LMVJV Waterfowl Working Group DATE: 30 June 2006 Attached is a revision of the table that estimates duck energy-days by habitat. Our revision includes changes made in response to comments received during discussions of the Working Group at the March and 27 June meetings in Vicksburg, MS. Note that duck energy-days in the table are estimates derived, in part, from data in another report to the Working Group prepared by Ken Reinecke and Bill Uihlein. That report provided new estimates of the daily energy requirements of ducks wintering in the LMVJV based on the average body mass and proportional abundance of dabbling ducks and wood ducks in population goals of the LMVJV rather than exclusively on the energy requirements of mallards. Please distribute this report to the Working Group and Joint Venture staff for their use.

2 2 Table 5. Carrying capacity of selected foraging habitats (expressed as duck energydays/ac [DEDs/ac]) for a hypothetical average dabbling duck (actually 7 species of dabbling ducks plus the wood duck) representing the proportional abundance of these species in the population goals of the Lower Mississippi Valley Joint Venture. For simplicity, we rounded estimates of food available and DEDs/ac to the nearest whole number but calculated all estimates using the most accurate data available. Food available True metabolizable Habitat (kg/ha) energy (TME; kcal/g) b DEDs/ac c Moist-soil 600 d 2.47 e 1,868 Harvested crops Rice 80 f 3.34 g 138 Soybean 60 h 2.65 g 36 i Corn g 505 j k Milo Unharvested crops Rice 5,240 l 3.34 g 23,833 Soybean 1,334 l 2.65 g 4,677 Milo 3,811 l 3.49 k 18,046 Corn 5,716 l 3.67 g 28,591 Japanese millet 1,500 m 2.61 n 5,203 Bottomland hardwoods 30% red oak 79 o 2.76 p % red oak 91 o 2.76 p % red oak 104 o 2.76 p % red oak 116 o 2.76 p % red oak 128 o 2.76 p % red oak 141 o 2.76 p % red oak 153 o 2.76 p % red oak 166 o 2.76 p 439 a To convert food available in kg/ha to lbs/ac, multiple kg/ha times b TME in units of kilocalories per gram (kcal/g) is determined by feeding different foods to captive ducks and determining how much energy they retain and use to meet daily energy requirements. c DEDs represent the average number of dabbling ducks (actually 7 species of dabbling ducks plus the wood duck) that can obtain daily energy requirements from an

3 3 acre (ac) of foraging habitat for a day. The simplest way to calculate DEDs/ac is to first calculate DEDs/ha, then transform the result from DEDs/ha to DEDs/ac. The following text describes the necessary steps. To calculate DEDs/ha, first subtract 50 kg/ha from the number of kg/ha of food available in a foraging habitat. We do this because ducks apparently give up feeding in habitats when finding food becomes difficult but before all the food is gone. Then, multiply the result of the preceding subtraction times 1,000, which is the number of grams per kilogram (g/kg). The result is grams per hectare (g/ha) of available food. Then, multiple the g/ha of available food times the average TME available per gram of food (kcal/g). The result is in units of kcal/ha. Next, divide the number of kcal/ha by the number of kcal required per day. In the case of dabbling ducks, we have adopted a value of kcal/day as a good approximation based on another report to the Waterfowl Working Group. Then, calculate DEDs/ha by dividing the kcal/ha of energy in a foraging habitat by the kcal/day of energy required by an average dabbling duck. Written as a formula, the calculation of DEDs/ha is ( kg food / ha 50 kg / ha) (1,000 g / kg) ( kcal TME / g) ( kcal TME required / duck day ) kcal / ha kcal / duck day DEDs / ha Multiplying DEDs/ha times converts DEDs/ha to DEDs/ac. In cases where more than one food is available in a foraging habitat, DEDs are calculated as a sum of DEDs for the different foods. For example, bottomland hardwoods provide acorns, invertebrates, and some moist-soil seeds, and all are included in estimates of available food and DEDs. d Our estimate of food availability in moist-soil wetlands is a judgment that summarizes data on abundance of seeds, tubers, and aquatic invertebrates. In making this judgment, we considered the overall mean (i.e., 496 kg/ha) for seed and tuber availability from Penny (2003) and Kross (2006), potential negative biases (i.e., 10-20%) in the preceding estimates identified by Reinecke and Hartke (2005), and availability of invertebrates in moist-soil habitat in winter reported by Duffy and LaBar (~19 kg/ha; 1994) and Gray et al. (~4 kg/ha; 1999). e Mean for moist-soil seeds fed to mallards (Kaminski et al. 2003). f Based primarily on Stafford et al. (2006). g Based on data for mallards (Reinecke et al. 1989). h No research data are available; we assumed an average 5% seed loss during harvest as suggested by Mayeaux et al. (1980). i Use of this value requires the judgment of managers and biologists. We based our estimate on data collected recently in Nebraska by Krapu et al. (2004). However, we arbitrarily decreased the values they reported ( kg/ha) to a more conservative 150 kg/ha because we believe our warm humid climate results in increased losses of grain lying on the ground after harvest. Research initiated recently by the University of

4 4 Tennessee should provide additional guidance on this issue in the next few years. j The only data we are aware of for availability of milo seeds after harvest is from a study in Texas during the 1980s (Iverson et al. 1985). Because no recent data or research in the Joint Venture area is available and we suspect waste milo deteriorates more rapidly in our warm humid climate than in Texas, we used a conservative value of 150 kg/ha rather than an average of the values ( kg/ha) reported by Iverson et al. (1985). As for corn, research initiated by the University of Tennessee should provide additional guidance in coming years. k Data for blue-winged teal (Sherfy et al. 2001), as no milo data exist for mallards. l Estimates of food available in unharvested crops are from E. J. Larson (Grain Crops Specialist, Mississippi State University, unpublished data; corn = 6,000 lbs/ac; milo = 4,000 lbs/ac; soybean = 1,400 lbs/ac; rice = 5,500 lbs/ac) and assume that grain in the field contains about 15% moisture and unharvested crops provide about 20% less grain in early winter than fields harvested in late summer or fall because decomposition and wildlife depredation occur before waterfowl arrive. m Data in the literature are limited; this value is the best personal assessment of K. J. Reinecke and R. M. Kaminski. n Mean based on data for mallards (Reinecke et al. 1989, Checkett et al. 2003) and blue-winged teal (Sherfy et al. 2001). o Hardwood bottomlands provide 3 food sources: invertebrates, moist-soil seeds in forest openings, and acorns. We assumed food availability in hardwood bottomlands included an average of 11.4 kg/ha (dry) invertebrates (calculated as a mean of data from the MAV in Table 2 of Batema et al. [2005]), 30.0 kg/ha of moist-soil seeds (i.e., assuming 5% of hardwood bottomlands are openings with food availability similar to moist-soil habitat [0.05 x 600 kg/ha; Table 5]), and an amount of acorns proportional to the percentage of red oaks in the forest canopy. To estimate availability of acorns, we used data from a long-term study in Missouri, where a forest with 80% of its basal area in red oaks produced an average 142 kg/ha (wet weight) of acorns. Because acorns contain about 30% water and TME for acorns was determined on a dry matter basis (Kaminski et al. 2003), we used 99.4 kg/ha for acorn availability in areas with 80% red oaks. For forests with other percentages of red oaks, we calculated availability of acorns proportional to availability in forest stands with 80% red oaks. p Acorns are the predominant food in bottomland hardwoods and the mean TME of 4 species of acorns fed to mallards and wood ducks (Kaminski et al. 2003) was used to represent the TME of all foods in bottomland hardwoods.

5 5 REFERENCES CITED Batema, D. L., R. M. Kaminski, and P. A. Magee Wetland invertebrate communities and management of hardwood bottomlands in the Mississippi Alluvial Valley. Pages in L. H. Fredrickson, S. L. King, and R. M. Kaminski, editors. Ecology and management of bottomland hardwood systems. University of Missouri- Columbia, Gaylord Memorial Laboratory Special Publication No. 10, Puxico, Missouri, USA. Checkett, J. M., R. D. Drobney, M. J. Petrie, and D. A. Graber True metabolizable energy of moist-soil seeds. Wildlife Society Bulletin 30: Duffy, W. G., and D. J. LaBar Aquatic invertebrate production in southeastern USA wetlands during winter and spring. Wetlands 14: Gray, M. J., R. M. Kaminski, G. Weerakkody, B. D. Leopold, and K. C. Jensen Aquatic invertebrate and plant responses following mechanical manipulations of moist-soil habitat. Wildlife Society Bulletin 27: Iverson, G. C., P. A. Vohs, and T. C. Tacha Habitat use by sandhill cranes wintering in western Texas. Journal of Wildlife Management 49: Kaminski, R. M., J. B. Davis, H. W. Essig, P. D. Gerard, and K. J. Reinecke True metabolizable energy for wood ducks from acorns compared to other waterfowl foods. Journal of Wildlife Management 67: Krapu, G. L., D. A. Brandt, and R. R. Cox, Jr Less waste corn, more land in soybeans, and the switch to genetically modified crops: trends with important implications for wildlife management. Wildlife Society Bulletin 32: Kross, J Conservation of waste rice and estimates of moist-soil seed abundance for wintering waterfowl in the Mississippi Alluvial Valley. Thesis, Mississippi State University, Mississippi State, Mississippi, USA. Mayeaux, M. M., J. G. Marshall, G. Baskin, and P. R. Vidrine Reducing soybean harvest losses. Louisiana Agriculture 23: Penny, E. J Estimating moist-soil plant seed availability in the Mississippi Alluvial Valley. Thesis. Mississippi State University, Mississippi State, Mississippi, USA. Reinecke, K. J., and K. M. Hartke Research notes: estimating moist-soil seeds available to waterfowl with double sampling for stratification. Journal of Wildlife Management 69: Reinecke, K. J., R. M. Kaminski, D. J. Moorhead, J. D. Hodges, and J. R. Nassar Mississippi Alluvial Valley. Pages in L. M. Smith, R. L. Pederson, and R.

6 6 M. Kaminski, editors. Habitat management for migrating and wintering waterfowl in North America. Texas Tech University Press, Lubbock, Texas, USA. Sherfy, M. H., R. L. Kirkpatrick, and K. E. Webb Nutritional consequences of gastrolith ingestion in blue-winged teal: a test of the hard-seed-for-grit hypothesis. Journal of Wildlife Management 65: Stafford, J. D., R. M. Kaminski, and K. J. Reinecke Waste rice for waterfowl in the Mississippi Alluvial Valley. Journal of Wildlife Management 70:61-69.