Role of glucose supplementation on physiology and metabolism of a nocturnal migrant (Emberiza bruniceps) under laboratory conditions.

Glucose is the simplest sugar and the ultimate source of energy for the cells. In the present study, we have tried to investigate the plausible role of glucose on seasonal physiology of redheaded bunting such as: hyperphagia, initiation and persistence of migratory restlessness, life history state-dependent plasma metabolite profile and fuel preference during migratory phenotype. Buntings are photosensitive species and exposure to short (8 L:16D) and long (13 L:11D) photoperiod leads to simulation of non-migratory and migratory life history states, respectively, in these birds. For experiment, birds were divided into three groups (N = 5 each), where, group I served as control, group II and III received 5% and 15% glucose (w/v), respectively, in drinking water. Our results clearly demonstrate the role of glucose in early initiation of zugunruhe (migratory restlessness) followed by its sustenance for longer duration of time. Food intake was inversely proportional to glucose concentration; however, water intake was substantially high for birds of 5% glucose group. Besides these, the circulating plasma concentration of glucose, triglycerides and cholesterol were significantly high because of external glucose supplementation. The study also provides the evidence of non-dependence of fat alone in fueling the migratory journey. Thus, the current study clearly illustrates the role of glucose in different life history states of migratory redheaded bunting.