sex differences in the mechanism of photoperiodic control of migratory fat deposition in chaffinches (Fringilla coelebs)

Comparative stugy of photoperiodic control of vernal migratory fattening in male and female chaffinches was carried out with the respect to sex differences in the time of vernal migration. When the chaffinches of both sexes were kept under natural day lenght on Courish Spit in the Baltic Sea (55 N), the deposition of fat in males began on the average 2-3 weeks earlier than in females. In experiments using skeleton photoperiods, the rhythms of photosensitivity causing fattening were detected in both sexes. The photoinducible phase of males lies somewhat earlier in night (by 1-1. 5h) than that of females, The results are discussed in the terms of different models elaborated to explain the circadian mechanism of photoperiodic control of migratory fattening.