Figure 2. Variation in plasma antioxidant capacity (z-standardised TAS
values) between blackcaps with different levels of multiple status of
infection by haemosporidian parasites. Estimates and 95% confidence
intervals were computed from a model controlling for uric acid content,
residual body mass, year and plasma MDA. The dots are individual
estimates, jittered horizontally to reduce overlapping.
Food preference and physiology
We obtained six models with ΔAIC ≤ 2 (Table 2), which were deemed
equally good to explain food preference. The model with lowest AICc
value included RBC oxidative stress, plasma-MDA (log-transformed), uric
acid and year. Given that the best model was not strongly weighted
against competitor models, we used a full model averaging of the six
models to obtain parameter estimates following (Symonds and Moussalli
2011). Plasma-MDA was the only physiological variable with a significant
effect on food preference: individuals with lower log-transformed
plasma-MDA preferred fat-enriched food (full model estimate ± adjusted
SE = -2.08 ± 1.04, P = 0.047) controlling for an effect of the
year (estimate ± adjusted SE = -1.99 ± 1.01, P = 0.049, all other
effects with P > 0.07).
Table 2. Selection of the best models to explain food preference as a
function of physiological parameters involved in oxidative status. The
models are arranged according to the Akaike Information Criterion
corrected by sample size (AICc), where the best model (number 1) is the
one with lowest AICc. Models with ΔAICc ≤ 2 are shown, indicating their
AICc value, the increase in AICc compared to the best model, the model
weight and the number of parameters. The same information is shown for
the null model (ranked 95) at the end of the table.