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Effect of the environmental variables on AIV cases in wild birds in the contiguous US, 2005-2008.
| Effect | Est. | Std. Err. | t-value (df = 132) | p |
|---|---|---|---|---|
| Intercept | -3.279 | 0.58 | -5.65 | <.0001 |
| First day of the year free of ice or snow Range: 0 (snow-free) to day of the year 150 | -0.0282 | 0.0116 | -2.43 | 0.0164 |
| Minimum temperature Range: -7.15 to 19.67°C | -0.2143 | 0.0734 | -2.92 | 0.0041 |
| Percent harvested cropland per county: Range: 0-100 | 0.0433 | 0.00951 | 4.56 | <.0001 |
