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Photoperiodic responses of a subtropical population of the finch zonotrichia capensis hypoleuca


, : Photoperiodic responses of a subtropical population of the finch zonotrichia capensis hypoleuca. Condor 76(3): 233-237

While the gonadal cycle of Zonotrichia capensis hypoleuca at 26.9.degree. S [latitude] is photoperiod-dependent and possibly under fairly strict photoperiodic control, the environmental factors that determine the precise time of breeding are unknown and probably complex. The factors that time the annual cycle are not entirely endogenous; predictive information is involved; control of the gonadal and molt cycles could be entirely exogenous, depending only on the actual oscillation in the photoperiod. There may be of a long-period rhythm in gonadal weight; this should be explored further under appropriately controlled conditions. It is probable that at least some relatively low-latitude populations of birds are capable of very fine discrimination of photoperiodic information, such that an approximately annual periodicity in testicular growth and collapse can be timed by the photocycle.

US$19.90

DOI: 10.2307/1366336


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