Binkley S, Mosher K, Reilly K B
Physiol Behav. 1983 Dec;31(6):829-37. doi: 10.1016/0031-9384(83)90280-9.
House sparrows, Passer domesticus, have circadian rhythms of locomotor activity that can be entrained by light-dark cycles. Perch-hopping activity was studied in house sparrows that were given control of their own lighting. In one series of experiments, sparrows permitted to select their own lighting most commonly chose circadian freerunning cycles. The period of the selected freerunning cycles was 23.2 hr (0.9 hr shorter than the period length the sparrows exhibited in constant dark). The average self-imposed "photoperiods" in the selected freerunning cycles ranged from 8.2-10.0 hr. In a second series of experiments, sparrows were exposed to LDLD1:6:1:16. This cycle can be interpreted ambiguously as the skeleton of a short photoperiod, LD8:16, or of a long photoperiod, LD18:6. All the birds (13 birds; 23 trials) interpreted the skeleton cycle as a short photoperiod because they entrained to it as they would to LD8:16.
家麻雀（Passer domesticus）具有可被明暗周期调节的昼夜运动节律。对能够自行控制光照的家麻雀的栖木跳跃活动进行了研究。在一系列实验中，被允许自行选择光照的麻雀最常选择昼夜自由运行周期。所选自由运行周期的时长为23.2小时（比麻雀在持续黑暗中表现出的周期长度短0.9小时）。所选自由运行周期中平均自我设定的“光周期”范围为8.2 - 10.0小时。在第二系列实验中，麻雀被暴露于LDLD1:6:1:16的光照周期下。这个周期可以被模糊地解释为短光周期LD8:16或长光周期LD18:6的框架。所有的鸟（13只鸟；23次试验）都将这个框架周期解释为短光周期，因为它们像对LD8:16一样被其调节。
