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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

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

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
  1. Bold entries highlight statistically significant effects, P < 0.05