Linear models of oxidative damage biomarkers in relation to sex, breeding stage and sampling date.

Where appropriate, models were run while controlling for heterogeneity of variances between levels of the fixed factors (see Materials and Methods for details). Terms shown in italics were removed from the model (see Materials and Methods for details).a: estimated mean values (s.e.): males, before laying = 1.81 (0.33), after laying = 0.74 (0.11); females, before laying = 3.62 (0.30), after laying = 0.81 (0.10).b: estimated slopes (s.e.): before laying = −0.06 (0.02), t = −2.71, P = 0.009; after laying = 0.01 (0.01), t = 0.99, P = 0.33.c: estimated mean values (s.e.): males = 1.43 (0.04); females = 1.77 (0.06).d: estimated mean values (s.e.): before laying = 1.51 (0.05); after laying = 1.69 (0.05).