Diurnal variations in serum metabolites of wintering redheaded buntings.

Daily behavioural and physiological changes in bird may reflect in biofluid metabolite composition. Locomotor activity, food intake and body temperature of group (n=7) of male migratory redheaded buntings held under short days (8L:16D, SD) were monitored besides blood sampling at midday (ZT4: 4 hours zeitgeber time starting ZT0 as lights 'on') and midnight (ZT16). The birds exhibited higher activity and increased feeding during daytime with negligible activity and feeding at night. Gas chromatography mass spectrometry and chemo-metric analyses of bird serum revealed higher levels of lipid (palmitic, oleic and linoleic acids) and protein (uric acid and proline) catabolites in daytime serum samples as compared to night samples. Higher night-time levels of short chain fatty acids indicated utilization of glucose and lipolysis in night fasted birds. High night-time levels of taurine, a sulphur amino acid has adaptive advantage to night migratory song birds. The diurnal differences in metabolite patterns suggests differential energy expenditure during day and renders survival benefit to buntings as night migrants. We propose a GCMS method that could be useful to unravel different annual life-history stages including migration.