Table 2.
Selection on body mass of breeding male and female red-billed gulls
| Parameter | N | Standardized directional selection differential |
Standardized quadratic selection differential |
||||
|---|---|---|---|---|---|---|---|
| Estimate ± SE | t | P | Estimate ± SE | t | P | ||
| Reproductive success | |||||||
| Males | 338 | −0.003 ± 0.08 | −0.043 | 0.97 | −0.051 ± 0.05 | −0.943 | 0.35 |
| Females | 213 | 0.107 ± 0.12 | 0.872 | 0.38 | 0.016 ± 0.09 | 0.173 | 0.86 |
| Fledging success | |||||||
| Males | 346 | 0.032 ± 0.045 | 0.722 | 0.471 | −0.052 ± 0.030 | −1.73 | 0.085 |
| Females | 213 | 0.104 ± 0.063 | 1.645 | 0.101 | 0.015 ± 0.044 | 0.343 | 0.732 |
Standardized selection differentials were estimated regressing relative estimate of lifetime reproductive success and lifetime fledging success against standardized mass according to the procedures described by Lande and Arnold (40).