Direction of correlation (positive, negative or absent, see column 1) between concentrations of a particular hormone (column 2: T, testosterone; E, oestradiol; A4, androstenedione; DHT, dihydrotestosterone; B, corticosterone; T4, thyroxine) in maternal plasma and egg yolks in 11 studies on several bird species (column 3: B-h., black-headed; B-b., black-backed). The type of data are indicated in column 5: individual females, correlation based on data from individual females and their eggs; group level, comparison of the effect of a manipulation (social challenge and food provisioning during egg laying) and artificial selection for adult plasma hormone levels on female plasma and yolk hormone concentrations; laying sequence, comparing the patterns of change in plasma and yolk over the laying sequence of a clutch. The last column refers to sampling protocol; see also text.