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Average yolk concentrations for the androgens (a) testosterone (T) and (b) 5α-dihydrotestosterone (5α-DHT for study species in endemic (i.e. not shared between North and South America) and clades (families or genera) of passerines that are shared between north temperate (Arizona, open bars) and tropical (Venezuela, filled bars) sites. Numbers above the bars reflect the numbers of species in the clade; the absence of a number indicates a sample of one species.
