habitat suitability index models: eastern wild turkey - USGS National ...

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Fig. 3a Fig. 3b 1.0 1.0 \D r-, :::- :::- ..... ..... (/') (/') 0.8 .......... 0.8 x Q) Q) "'0 "'0 t: 0.6 t: 0.6 ..... ..... >, >, ..... 0.4 ..... 0.4 ..... .... ..c ..c n::l 0.2 n::l 0.2 ..... ..... :::l (/') 0.0 0 25 50 75 100 Percent shrub crown cover (food production) x :::l (/') 0.0 0 25 50 75 100 Percent shrub crown cover (behavioral) Fig. 3c co 1.0 :::- ..... (/') 0.8 .......... x Q) "'0 t: 0.6 ..... >, ..... ..... ..... ..c n::l ..... :::l (/') 0.4 0.2 0.0 0 25 50 75 100 Percent of shrub crown cover comprised of soft mast producing shrubs Figure 3. The relationship between habitat variables used to assess the fall, winter, and spring food value of shrubs and sUitability indices for the eastern wild turkey. 16
Areas with shrub coverage of 80% or greater are assumed to be totally unsuitable for turkeys. The relationship between shrub cover related to the turkey's behavioral response and a suitability index (SIV7) is presented in Figure 3b. It is assumed that the best shrub conditions exist when 100% of the shrubs produce soft mast, and that low suitabilities will still be provided in areas with a lack of soft fruit producing shrubs, due to the turkey's use of other shrub plant parts for food. The relationship between the amount of soft fruit producing shrubs and a suitability index (SIV8) is presented in Figure 3c. The fa 11, wi nter, spri ng food value (FWSSIl) in forest and tree savanna cover types is equal to the combined values of tree and shrub mast, modified by overall shrub density. Tree mast may be provided by either soft or hard mast species, and it is assumed that tree mast and shrub mast are equal in value. Excessive shrub densities will detract from the value of all mast resources. These relationships can be expressed mathematically, as shown in Equation 3, for DFW, EF, DF, ETS, and DTS. FWSSII = (SIV4 + SIV5) + (SIV6 x SIV8) 2 x SIV7 (3) Note: When the sum of SIV4 + SIV5 exceeds 1.0, it should be reduced to 1.0 before computing FWSSI1. The fall, winter, spring food value (FWSSI2) in shrub cover types is equal to the amount of food producing shrubs, modified by overall shrub density and the distance to forest cover. Shrubs alone are assumed to be able to provide up to one-half of the total fall, winter, and spring food value. This relationship can be expressed mathematically, as shown in Equation 4, for ES, DS, ESS, and DSS. FWSSI2 = (SIV6 x SIV8) x SIV7 x SIV3 2 (4) Croplands may provide high quality fall, winter, and spring food for the eastern wild turkey, especially in the western and northern portions of the turkey's range. Corn and soybeans are highly preferred, while other grains are somewhat less valuable food sources. Crops other than corn, soybeans, and other grains are assumed to provide no food value. The relationship of the type of crop to a suitability index (SIV9) is presented in Figure 4a. The overwinter management of croplands will have a significant effect on the amount of crop food potentially available to turkeys. A direct measure of waste crop availability requires considerable field time and there is a large amount of variability in such measurements (Frederick et al. 1984). Therefore, a general approach is taken in this model to assess overwinter crop availability. Optimum conditions are assumed to exist in areas where more than 5% of the crop remains unharvested through the winter. Areas with the crop harvested 17
Page 1 and 2: BIOLOGICAL REPORT 82(10.106) AUGUST
Page 3 and 4: MODEL EVALUATION FORM Habitat model
Page 5 and 6: Biological Report 82(10.106) August
Page 7: PREFACE This document is part of th
Page 10 and 11: ACKNOWLEDGMENTS William M. Healy, G
Page 12 and 13: (Christisen and Korschgen 1955). Ma
Page 14 and 15: or depressions in the ground (Korsc
Page 16 and 17: Striped skunks (Mephitis mephitis),
Page 18 and 19: Iowa has reintroduced turkeys into
Page 20 and 21: Cover types. This model was develop
Page 22 and 23: ..--l Fig. 1a 1.0 1.0 ::::- ::::- .
Page 24 and 25: The amount of acorn mast produced i
Page 28 and 29: in the fall, but plowed in the spri
Page 30 and 31: Figure 5. The relationships between
Page 32 and 33: 0.2 a Fig. 6a 1. a -+---...........
Page 34 and 35: Habitat variable Li fe regu isite C
Page 36 and 37: Variable (definition) Percent canop
Page 38 and 39: SOURCES OF OTHER MODELS Williamson
Page 40 and 41: Hamrick, W. J., and J. R. Davis. 19
Page 42 and 43: Pack. J. C., R. P. Burkert. W. K. I
Page 44 and 45: 502n·101 REPORT DOCUMENTATION 11.
Page 46: DEPARTMENT OF THE INTERIOR u.s. FIS

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