Circadian Aspect of Photoperiodic Time Measurement in a Female House Sparrow, Passer domesticus

Abstract

Endogenous circadian rhythms are involved in various photoperiodic responses of birds. Investigations involving the mechanisms of photoperiodic time measurement in birds have been confined mainly to temperate zone species using males exclusively. Due to the paucity of experimental evidence on subtropical birds that have very wide distribution, the present study was performed using subtropical female house sparrows. Photoperiodic sparrows were subjected to various T cycles for 60 days in which a fixed 3-h photophase was combined with scotophase in cycles of 20-30 h duration. Simultaneously, two groups of birds were also exposed to short days (light:dark = 8L:16D) or long days (15L:9D) as controls. Significant ovarian growth was found only in cycles of 3L:17D, 3L:23D, 3L:25D, and 3L:27D as well as in 15L:9D, whereas no positive response was detected in 3L:19D, 3L:21D, and 8L:16D. Plasma levels of estradiol showed a close relation to ovarian growth. The results indicate that photoperiodic time measurement in house sparrows involves an endogenous circadian rhythm.

Effects of Photoperiod Alterations on Adrenocortical, Pineal and Gonadal Activity in Nocturnal bird, Athene brama and Diurnal bird, Perdicula asiatica

“…Under these conditions pineal gland activity responded in an opposite manner. Therefore, it is possible that the changes in photoperiod utilize pineal gland to mediate (Arendt, 1988;Glass, 1988;Haldar and Rai, 1997), as explained above or an endogenous circadian rhythm to entrain photoperiodic response in birds (Ravikumar et al, 1995) may be operative or else these two together mediate the photic stimuli (Glass, 1988). This phenomenon has to be explored further.…”