Table 2.

Variance–covariance matrix (with SE) of the parameters involved in bivariate random regression of clutch size and lifetime fledgling production (LFP) as a function of laying date. LFP was expressed as relative fitness, by dividing it with its phenotypic mean (mean fitness of 1). The diagonal presents the variances in elevation (ind₀), linear slope (ind₁), and quadratic slope (ind₂), and LFP. Covariances are below the diagonal. The last row therefore presents the selection differential (S) on the reaction-norm properties. Correlations are reported above the diagonal. Model log-likelihood is –342.19. Significance of selection was tested using a likelihood ratio test between this full model and the model where the respective element of the matrix was constrained to zero. The log-likelihood (LogL) of the constrained model and the test statistics is reported in the bottom part of the table, together with the intensity if selection (i.e., S divided by the standard deviation of the respective parameter). The denominator degrees of freedom cannot be estimated numerically for this model and were conservatively equaled to the number of individuals.

	Bivariate random regression (co)variances
	ind0	ind1	ind2	LFP
ind0	0.129 ± 0.041	–0.407 ± 0.23	0.346 ± 0.23	0.394 ± 0.11
ind1	–0.074 ± 0.043	0.260 ± 0.15	0.218 ± 0.33	–0.194 ± 0.16
ind2	0.099 ± 0.095	0.089 ± 0.13	0.645 ± 0.33	0.516 ± 0.18
LFP	0.104 ± 0.031	–0.073 ± 0.056	0.304 ± 0.092	0.539 ± 0.042
Fixed effect on clutch size		df (nom)	df (den)	F	P
μ	3.35 ± 0.079
Laying date	–0.060 ± 0.0031	1	361	379.4	<0.001
Age	1: –0.19 ± 0.14
	2: 0.027 ± 0.10	2	361	0.88	0.42
Fixed effect on LFP		df (nom)	df (den)	F	P
μ	1.54 ± 0.19
Cohort year		26	361	1.40	0.095
Parameter	Intensity of selection (i)	LRT
		LogL	χ2	df	P
ind0	0.29	–340.6	15.9	1	<0.001
ind1	–0.14	–335.0	1.83	1	0.17
ind2	0.38	–340.0	13.4	1	<0.001