Table 2. LMM of the influence of parental age on chick mass at hatching.
| Term | d.f. | Effect | s.e. | Wald stat (χ2) | P value |
|---|---|---|---|---|---|
| Day | 1 | −0.008883 | 0.0010602 | 70.19 | <0.001 |
| Clutch number | 1 | −0.9716 | 0.04027 | 582.10 | <0.001 |
| Within clutch order | 1 | −4.175 | 0.0929 | 2021.61 | <0.001 |
| within clutch order2 | 1 | 1.518 | 0.0995 | 232.89 | <0.001 |
| Maternal age | 1 | 33.12 | 1.172 | 798.67 | <0.001 |
| Maternal age2 | 1 | −2.245 | 0.0841 | 712.17 | <0.001 |
| Paternal age | 1 | 1.334 | 0.7418 | 3.23 | 0.072 |
| Paternal age2 | 1 | −0.08959 | 0.051134 | 3.07 | 0.080 |
d.f., degree of freedom; LMM, Linear Mixed Model; s.e., standard error.
The aim of the analysis was to examine the potential influence of parental aging on the hatching mass of their offspring. A LMM was implemented with chick mass at hatching as the response variable; constant=−84.06. In total, the analysis includes assessments of 41,844 chicks produced by 2,488 females and fertilized by 1,140 different males. Parental identity and year of breeding were controlled as random effects. Variables derived from parental age and clutch sequences data were loge transformed to improve model fit.
Numbers in superscript indicate that the terms have been fitted as a second order polynomial.