Table 1. Mean number of waterbirds during the non-breeding period in the Odra River Estuary (NW Poland); standard error and confidence intervals, taking into account the method and weather conditions (ice =0 − no ice, ice =1 − ice cover over 70%).
| Method | Ice | Mean | Standard error | Confidence intervals 95% | |
|---|---|---|---|---|---|
| Lower limit | Upper limit | ||||
| Aircraft | 0 | 3,907.064 | 653.361 | 2,622.483 | 5,191.645 |
| 1 | 1,848.523 | 480.258 | 904.283 | 2,792.764 | |
| Land | 0 | 4,323.867 | 706.905 | 2,934.012 | 5,713.722 |
| 1 | 944.410 | 341.824 | 272.346 | 1,616.475 | |