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Cofrin Center for Biodiversity

An Ecological Index of Forest Health Based on Breeding Birds

By: Erin E. Gnass Giese, Dr. Robert Howe, Dr. Amy Wolf, Nicholas Miller, and Nicholas Walton

Click to go to introduction. Link to introduction. Click to learn more about Indicies of forest health. Link to IEC Explained. Click to download the calculator. Link to the IEC calculator. Click to go to IEC instructions. Link to calculator instructions.

Instructions on How to Use the IEC Calculator

Before using the IEC calculator, please read these instructions carefully.

Understanding the IEC Calculator Spreadsheet Download

Tabs in the IEC Calculator spreadsheet:
- Instructions – instructions on how to use the IEC calculator and metadata
- CalcQ – calculator for estimating an IEC score for a group of sites or management area using frequency data
- CalcPA – calculator for estimating an IEC score for a single site using presence/absence data
- SppCodes – list of species 4-letter alpha codes, common names, and scientific names
- BirdBR – list of biotic response (BR) function parameters (mean (M), SD (standard deviation), and H (height)), which use a normal distribution function, for the 38 indicator bird species

For tabs CalcPA and CalcQ, only cells highlighted in blue (Observed data) may be changed by entering collected bird data (see Download Calculator).  Cells under gray highlighted column headers contain parameters for all bird BR functions needed for IEC calculation. These have been previously determined by Gnass (2012) and should not be altered. If you wish to add species or use different BR functions (easily accomplished if background data or subjective valuation criteria are available), contact us for guidance.

Calculating Index of Ecological Condition (IEC) Scores

Step 1:  Download and open the IEC calculator.

Step 2
:  Install the Solver add-in.

Step 3:  Enter collected bird point count data (including flyovers) in the Observed column for species listed in the first column (e.g., AMCR, AMRE, etc.). A key to 4-letter species codes is given in the SppCodes tab.  Observations of species not listed are ignored. Screenshot images of steps provided using MS Excel 2010.

Two options are available for entering bird data and calculating the IEC:

 1 - If your data have been collected from a single count at a single site, use the CalcPA tab.  Enter the number of individuals or simply 1 (=present) or 0 (=absent) for each species in the Observed column (highlighted in blue).

data entry screenshot showing observed column.

2 - If your data consist of multiple point counts at a site or multiple counts in an area of interest, use the CalcQ tab.  Enter the proportion of point counts for which each species was observed (i.e., frequency = # of counts a species was observed / total # of counts) in the Observed column (highlighted in blue).

Screenshot of step 3b.

Step 4:  Set an initial “guess” for the numeric IEC score to 5 (cell 04, for both tabs, highlighted in yellow). 

Step 5a
:  Calculate the IEC score by opening Solver, clicking Solve in the Solver Parameters window.  Note:  although the steps provided display the CalcQ tab, the steps are identical for both CalcPA and CalcQ tabs.

screenshot of step LSQ 5a.

Step 5b: After clicking Solve in the Solver Parameters window click OK in the Solver Results window.Note:  although the steps provided display the CalcQ tab, the steps are identical for both CalcPA and CalcQ tabs.

Screenshot of LSQ step 5b.

Step 6:  The IEC score (0-10) will now appear in cell 04 in either tab. If you are calculating scores for multiple sites or landscapes, record the result and repeat steps 3-5 for a new site or group of sites.

Screenshot of LSQ step 6.

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