Table 2.
Individually marked females observed on the water, alone or in pairs, with known birth nestmates or with other marked females
| Area and year | N (number of marked females observed) | Np [number of possible pairs N(N − 1)/2] | Nr (maximum number of nestmate pairs) | nm (number of pairs of marked females observed) | nr (number of nestmate pairs observed) |
|---|---|---|---|---|---|
| U 1986 | 5 | 10 | 3 | 1 | 1 |
| U 1987 | 13 | 78 | 4 | 6 | 1 |
| J 1989 | 15 | 105 | 2 | 4 | 1 |
| J 1990 | 11 | 55 | 4 | 1 | 0 |
| U 1990 | 10 | 45 | 1 | 3 | 1 |
Nr is the number of pairs of birth nestmates that can be formed among the observed marked individuals for the relevant area and year. There may be additional birth nestmate pairs not known to us among the females. Because known nestmates are overrepresented among the observed pairs, unknown nestmates are also expected to be overrepresented (compared to unrelated birds) among the observed pairs. The fact that unknown nestmates will not be recorded as such therefore tends to make the test conservative).