Table 3.
Results of bird-window collision surveys. Raw counts and bias-adjusted estimates of fatal collisions by month based on collision surveys in Stillwater, Oklahoma, USA in 2015–2016.
| Month | Number of surveys | Number of carcasses | Number of feather piles | Total count | Seasonal bias | Adjusted carcasses | Adjusted total count | Adjusted total per survey |
|---|---|---|---|---|---|---|---|---|
| Jan | 56 | 0 | 1 | 1 | 0.680 | 0.0 | 1.5 | 0.027 |
| Feb | 56 | 0 | 0 | 0 | 0.680 | 0.0 | 0.0 | 0 |
| Mar | 79 | 3 | 0 | 3 | 0.680 | * | * | * |
| Apr | 982 | 24 | 5 | 29 | 0.883 | 27.2 | 32.8 | 0.033 |
| May | 1004 | 92 | 13 | 105 | 0.883 | 104.1 | 118.9 | 0.118 |
| June | 879 | 41 | 16 | 57 | 0.905 | 45.3 | 63.0 | 0.072 |
| July | 985 | 17 | 6 | 23 | 0.905 | 18.8 | 25.4 | 0.026 |
| Aug | 925 | 13 | 13 | 26 | 0.905 | 14.4 | 28.7 | 0.031 |
| Sep | 886 | 39 | 10 | 49 | 0.758 | 51.4 | 64.6 | 0.073 |
| Oct | 970 | 49 | 3 | 52 | 0.758 | 64.6 | 68.6 | 0.071 |
| Nov | 94 | 15 | 2 | 17 | 0.680 | * | * | * |
| Dec | 65 | 1 | 0 | 1 | 0.680 | 1.5 | 1.5 | 0.023 |
Bias adjustments incorporate seasonal estimates of searcher efficiency and scavenger removal rates of bird carcasses, and adjusted total counts are based on applying bias adjustments to raw counts excluding feather piles.
*Surveys in March and November occurred more frequently than calculated in bias adjustments, so adjusted values would be overestimated for those months.