Best models explaining the relationships between chromatic and achromatic contrasts of nestling gape traits against each other or against the nest background and variables reflecting level of nestling competition (broodr: brood reduction; lgCS: log transformed clutch size; lgNP: log transformed nes

Results are from Phylogenetic Generalized Least Squares analyses (PGLS). The best models were selected from the Akaike's criterion. We show the corrected AIC'\s value (AICc), the Akaike Weights estimated from the 31 possible models (W31), and the Evidence Ratios of each model. Furthermore, we also show percentage of variance (R2(adjusted)) explained by each model (i.e., those with AICc values differing less than 2 from the AICc value of the best model), as well as beta(SE) values associated to each of the independent variable in the model. When nesting habits (hole vs non hole) appeared in the tested models, effect size (+/− confidence intervals (95%)) estimated with F-values from the ANOVA code in PGLS were reported.