Meeting Abstract
Study on ecological consequences of night-light (NL) has received great interest in last decade. The pattern of NL may vary with the geographical region and its night-life. It may be available as high intensity light throughout night or in short durations breaking the night into ‘part night’ which could be critical for a nocturnal migrant in timing its migration and reproduction. We tested this in controlled laboratory environment by exposing the migratory redheaded bunting (Emberiza bruniceps), a long distance Palaearctic-Indian migrant overwintering in India, to NL at different phases of night. Winter daylengths are not stimulatory for buntings but increasing daylengths of spring prepare them for vernal migration and subsequent reproduction. Four groups of male buntings captured from overwintering flock were transferred to individual activity cages and maintained under non-stimulatory short days (8L:16D; L = 100lux, D = 0.1lux) for 2 weeks. Later, they were given urban night-light (NL) environment (~2lux light intensity) for 4hours (4h) in continuation with onset of night (early night; ZT 08-12; group 1, ZT0= zeitgeber time 0, time of lights on), at mid-night (ZT 14-18; group 2) or preceding the day’s onset (ZT 20-24; group 3), or for 16h (ZT 08-24; group 4) throughout night. Birds in all groups showed intense nighttime activity, altered melatonin and temperature rhythms, increase in body mass and body fattening, food intake and gonadal size in otherwise non-stimulatory daylengths suggesting that NL changes the perception of daylengths longer than they actually are. This information may be valuable in adopting part-night lighting approach to help reduce the physiological burden such as early migration and reproduction, of artificial lighting on the nocturnal migrants.
