Photoperiodic regulation of seasonal responses in Indian weaver bird (Ploceus philippinus)

Abstract

Photoperiod (=day length) is the vital factor for the regulation of behavioral and physiological activities in many avian species. This study investigated the seasonal cycles of testicular growth and secondary sexual characteristics of Indian weaver bird under natural day length (NDL) and the effects of duration and intensity of light on photoperiodic induction. In the first experiment, groups of birds (n = 7 each) were exposed to under NDL in April 2008 and May 2009 for 8 and 12 months, respectively. In second and third experiment, birds (n = 6 each group) were exposed to different photoperiods (11.5L:12.5D, 12L:12D, 13L:11D, and 15L:9D) at the same (500 lux) light intensity, and to 13L:11D at different light intensities (10-, 50-, 500-, and 800-lux). Observations on testis size, molt, and plumage score were recorded 2-week (molt and plumage) or at 4-week intervals (testes). Both the NDL groups showed similar seasonal cycles of testicular growth-regression and secondary sexual characteristics. Second and third experiments suggest that the photoperiodic induction was depending upon duration and intensity of the light. Birds showed testicular growth-regression cycle followed by molt and plumage color change only under 13L:11D and 15L:9D and only 500-and 800-lux under 13L:11D photoperiod but not under 11.5L:12.5D and 12L:12D and 10-and 50-lux light intensities. Pre-and postnuptial molting on body feathers were progressed with gonadal stimulation-maturation and regression cycle under 13L:11D and 15L:9D. Results under different lightdark cycles suggest that day length of about 12 h or more and above the threshold level of light intensity are essential for the induction of photoperiodic responses.

Effects of thyroid hormone manipulation on pre-nuptial molt, luteinizing hormone and testicular growth in male white-crowned sparrows (Zonotrichia leuchophrys gambelii)

“…Since, Rowan (1925) first identified that gonadal development in birds breeding at mid to high latitudes was triggered by increasing day length, photoperiodic regulation of avian behavior and breeding has been of continuing interest to researchers. Increasing spring photoperiod has been shown to initiate both pre-nuptial molt and to trigger gonadal development in birds ( Dawson, 1999 , Dawson, 2002 , Dawson et al, 2001 , King, 1968 , Lesher and Kendeigh, 1941 , Pandey and Bhardwaj, 2015 ). As pre-nuptial (also termed pre-alternate) molt is not observed in all species, control mechanisms remain obscure and it is often overlooked in studies of molt in favor of the more common and robust post-nuptial (also termed pre-basic) molt.…”

A review of Baya Weaver Ploceus philippinus (Linnaeus, 1766) (Aves: Passeriformes: Ploceidae): ecological and conservation status

“…A pre-nuptial molt occurred between March and June and a post-nuptial molt between October and November (Narasimhacharya et al 1987). The lightning of the bill color starts to cause in August and its turns to a complete straw color in November and depigmented their plumage to the non-breeding type (Rani et al 2007;Pandey & Bhardwaj 2015). The alteration in night light as a bright light during the night alters the resting pattern J TT of this bird it induced a fragmented activity in the early phase of night and enhancement at late night instead of the actual onset of the day (Raap et al 2015;Touitou et al 2017;Kumar et al 2018).…”