A consistent long-lasting pattern of spatial variation in egg size and shape in blue tits (Cyanistes caeruleus)

Table 1 Summary of linear mixed models of egg volume of blue tits in relation to year, site and clutch size. Two separate models are shown: (i) with year as a categorical factor and (ii) with year as a continuous variable. Clutch ID included as a random effect

Effect	b-Estimate ± SE	df	F	P
Year as a categorical variable
Final model
Intercept	1.207 ± 0.022	1;883.5	3927.5	< 0.0001
Year	Multiple estimates	11;760.2	1.3	0.239
Site	−0.056 ± 0.006	1;762.7	71.7	< 0.0001
Clutch size	−0.0042 ± 0.0017	1;884.6	6.2	0.013
Deleted terms
Site x Clutch size		1;753.9	1.3	0.330
Year x Site		11;739.9	1.3	0.212
Year x Clutch size		11;804.0	1.6	0.098
Year as a continuous variable
Final model
Intercept	5.306 ± 1.998	1;776.5	7.0	0.008
Year	−0.002 ± 0.0009	1;776.5	4.2	0.040
Site	−0.059 ± 0.006	1;777.8	87.1	< 0.0001
Clutch size	−0.002 ± 0.002	1;793.3	1.8	0.180
Deleted terms
Site x Clutch size		1;782.9	1.2	0.259
Year x Site		1;776.9	1.9	0.164
Year x Clutch size		1;790.4	2.7	0.101

ISSN: 1742-9994