EFFECTS OF DURATION AND TIME OF FOOD AVAILABILITY ON PHOTOPERIODIC RESPONSES IN THE MIGRATORY MALE BLACKHEADED BUNTING (EMBERIZA MELANOCEPHALA)

Abstract

SUMMARY The effects of the duration and time of food availability on stimulation of the photoperiodic responses (fattening and gain in body mass, and growth and development of testes) were investigated in the migratory blackheaded bunting(Emberiza melanocephala). Two experiments were performed. Experiment 1 examined the effects of a reduction in the duration of food supply in buntings that were subjected to long day lengths (16 h:8 h L:D) and received food ad libitum (group I) or for restricted durations, coinciding with the end of the lights-on period, of 8 h (group II) and 4 h (group III). Buntings of group I gained in body mass, whereas there was a mixed response in group II (half the birds gained and half lost body mass), and all birds of group III lost body mass. There was no effect on testis growth in groups I and II, but testes grew more slowly in group III. Experiment 2 investigated the effects of both the duration and the time of food availability. Of five groups of birds, group I was exposed to an 8 h:16 h L:D photoperiod, and groups II-V were exposed to 16 h:8 h L:D. Whereas birds of groups I and II received food ad libitum, those of groups III-V were fed only for 5 h, at zt 0-5(group III), zt 5.5-10.5 (group IV) or zt 11-16 (group V), where zt =zeitgeber time and zt 0 refers to the beginning of the lights-on period. Apart from duration, the timing of food availability also had an effect on photoperiodic stimulation under the 16 h:8 h L:D photoperiod. Birds that were fed ad libitum fattened and gained in body mass, whereas among restricted feeding groups, only birds in the group fed during the first 5 h(zt 0-5, group III) showed a significant increase in body mass (albeit considerably lower than in the ad libitum group). Birds fed during the middle 5 h (zt 5.5-10.5, group IV) showed an intermediate response, and those fed during the last 5 h (zt 11-16, group V) lost body mass. Testicular growth was suppressed in birds that were fed for 5 h in the evening, but not in those fed for the same period in the morning or in the middle of the long day. Taken together, these results show that the duration of food supply and/or the time of day at which food is available affect photoperiodic stimulation of fattening and gain in body mass as well as the growth and development of gonads in the blackheaded bunting.

Impact of Light at Night Is Phase Dependent: A Study on Migratory Redheaded Bunting (Emberiza bruniceps)

“…Body mass was recorded using a top pan balance up to an accuracy of 0.1 g. The food intake (g)/bird/day was measured as described by Kumar et al (2001). It was calculated as the difference between the food supplied and food recovered after 24 h. Body fattening (fat deposition in furcular, scapular, and abdominal areas) was assessed as the fat score on a scale of 0-5, where 0 represents no fat and 5 represents the maximum deposition of fat (Kumar et al, 2001).…”

“…Body mass was recorded using a top pan balance up to an accuracy of 0.1 g. The food intake (g)/bird/day was measured as described by Kumar et al (2001). It was calculated as the difference between the food supplied and food recovered after 24 h. Body fattening (fat deposition in furcular, scapular, and abdominal areas) was assessed as the fat score on a scale of 0-5, where 0 represents no fat and 5 represents the maximum deposition of fat (Kumar et al, 2001). The testis size was measured by laparotomy performed under general anesthesia (Kumar et al, 2002) using the formula 4/3 π ab 2 , where a and b denote one-half of long (length) and short (width) axes, respectively (Kumar et al, 2002).…”

Nocturnal melatonin levels decode daily light environment and reflect seasonal states in night-migratory blackheaded bunting (Emberiza melanocephala)

“…Before beginning an experiment, birds were weighed on a top pan balance to an accuracy of 0.1 g and laparotomized. 24 Testis volume was calculated using the formula 4/3πab 2 , where a and b denote half of the long (length) and short (width) axes, respectively. 24 Photosensitive (short day) or photorefractory (long day) birds lacked visible fat deposits and had small reproductively inactive testes.…”

Seasonality in tropical birds

“…Time‐restricted feeding negatively affects reproduction in birds. For example, during 3 weeks of exposure to a 16‐h photoperiod with food restriction for 5 h in the evening, testis recrudescence was observed in migratory black‐headed buntings ( Emberiza melanocephala ; Kumar et al, 2001). In house sparrows, experiments had shown enhanced testes size when birds were exposed to long photoperiods but not in short days and NDL.…”