Sources for yolk testosterone used in this study.

Mean yolk testosterone concentrations in core eggs, marginal eggs and the difference in yolk testosterone between core and marginal eggs. Marginal eggs represent the later-laid, asynchronously-hatching eggs and were identified by dividing the hatching spread by the laying interval between subsequent eggs (app. C). If these calculations produced non-integers, we rounded the values up. Core eggs represent the early-laid, synchronously-hatching eggs and were identified by subtracting the number of marginal eggs from the average clutch size. Yolk testosterone concentrations for core and marginal eggs were averaged to produce mean core T concentrations and mean marginal T concentrations, respectively. In our analyses, we included mean marginal T minus mean core T as a response variable and mean core T as a covariate that corrects for differences in average clutch T values across species as well as assay differences. * indicates the species excluded from analyses containing initial size asymmetries between core and marginal chicks as a predictor (n=28 species included). **indicates the species excluded from analyses containing hatching spread and logistic growth rate constant as a predictor (n=25 species included).