Fig. 1.

The presence of siblings is associated with a reduction in offspring honesty. Data points represent species’ mean correlation coefficients of long-term need and begging intensity for species where parents rear only one (n = 6 species) or more than one offspring per brood (n = 54 species). Positive correlations indicate that offspring in worse condition beg more intensely, providing honest information about need. Gray lines represent the 95% CIs from the model, run on the full dataset, controlling for phylogeny and repeated measures. Species with siblings present have a weaker correlation between need and begging, suggesting less honest signaling of need (Wald = 6.69, P = 0.0097).