Table 2.
Predictor weights calculated as the sum of the Akaike weights for each mixed‐effects logistic regression explaining variation in probability of giving birth to a foal surviving to late summer (n horse = 113, n observations = 496) or probability of weaning a foal (survival to year t + 1; n horse = 113, n observations = 321) in which that variable appeared
| Predictor | Analysis | |
|---|---|---|
| Probability of giving birth | Probability of weaning | |
| Repro t − 1 | 1.00 | 0.93 |
| Female quality | 0.95 | 1.00 |
| Female age² | 0.96 | 1.00 |
| Location | 0.00 | 0.01 |
| Density | 1.00 | 0.98 |
| Band size | 1.00 | 0.94 |
| Local sex ratio | 0.45 | 0.43 |
| Band sex ratio | 0.97 | 0.80 |
| Winter severity t − 1 | 0.55 | – |
| Winter severity | 0.82 | 0.67 |
| Winter severity t + 1 | – | 1.00 |
| Female quality: Repro t − 1 | 0.73 | 0.58 |
| Female age²: Repro t − 1 | 0.92 | 0.19 |
| Location: Repro t − 1 | 0.00 | 0.00 |
| Density: Repro t − 1 | 0.43 | 0.28 |
| Band size: Repro t − 1 | 0.37 | 0.27 |
| Local sex ratio: Repro t − 1 | 0.12 | 0.21 |
| Band sex ratio: Repro t − 1 | 0.38 | 0.37 |
| Winter severity t − 1: Repro t − 1 | 0.14 | – |
| Winter severity: Repro t − 1 | 0.22 | 0.17 |
Models included a combination of the following factors: female quality, female age, location on the island, local density, band size, band sex ratio, winter severity, and their interaction with reproductive status as fixed effects and horse identity as a random factor. Variables retained in the selected model are in bold.