Fig. 2. Pattern of circulating vitellogenin (VTG) measured daily during experiment 1. Horizontal lines indicate significant differences between VTG levels in birds measured on different days. Values are means + S.E.M. `Day' corresponds to day in Fig. 1A. NB refers to non-breeding values. ^**P<0.005, ^***P<0.0005. Vitellogenin plasma levels for days 2–6 were all significantly different from NB values (P<0.0005 in all cases).