Table 2.
Models analysing factors affecting egg volume and fledging success in meadow pipits.
| egg size | fledging success | |||||
|---|---|---|---|---|---|---|
| fixed term | W | d.f. | p | W | d.f. | p |
| altitude | 14.02 | 1 | <0.001 | 0.35 | 1 | 0.552 |
| breeding density | 0.24 | 1 | 0.624 | 0.21 | 1 | 0.646 |
| clutch size | 0.67 | 1 | 0.411 | 1.65 | 1 | 0.199 |
| year | 0.42 | 1 | 0.519 | 0.00 | 1 | 0.982 |
| replicate | 1.30 | 5 | 0.262 | 0.38 | 5 | 0.864 |
| year×replicate | 1.14 | 4 | 0.337 | 0.50 | 4 | 0.739 |
| lay date | 2.96 | 1 | 0.085 | 0.06 | 1 | 0.802 |
| (lay date)2 | 0.29 | 1 | 0.588 | 1.19 | 1 | 0.274 |
| sheep density | 6.81 | 1 | <0.01 | 1.82 | 1 | 0.177 |
| treatment | 1.29 | 2 | 0.274 | 1.90 | 2 | 0.150 |
| egg size | — | — | — | 0.07 | 1 | 0.785 |
Egg volume data were fitted to a linear mixed model; fledging success data (i.e. number of eggs that produce a nestling that fledges) were fitted to a generalized linear mixed model, with a binomial distribution and logit link function. Fixed terms were fitted sequentially. The significance of the scaled Wald statistics (W) was assessed using F-tests (with denominator degrees of freedom set at 15 by the experimental design) for altitude, breeding density, year, year×replicate, sheep density and treatment, and using chi-squared tests for clutch size, lay date and egg size effects, as there was considerable replication at the nest level. n=82 nests.