Table 1.

Final linear mixed model at the population level of the environmental determinants of mean laying date in tree swallows (n = 392). Environmental variables have been standardized prior to the analysis. Year was included as random effect. Adjusted R² for fixed effects was 0.182

Variable	Estimate	SE	d.f.	t-value	P-value
Intercept	141.415	0.658	8.1	215.01	<0.001
Latitude	0.479	0.195	376.9	2.46	0.014
Breeder density	−1.469	0.205	383.4	7.16	<0.001
Temperature	−0.929	0.341	158.5	2.73	0.007
Temperature × Breeder density	−0.450	0.204	379.6	2.20	0.028