Daily and fasting variation in blood parameters and H/L ratio in House Sparrow (Passer domesticus)

Fluctuations in food supply are frequent in nature during seasons, in different stages of annual cycle of animals, and lately, climate change has become a strong driving force that could affect food supply. An animal's capacity to resist fasting is, therefore, determined by its ability to store energy and control its allocation during periods of food restriction. Daily variations of metabolic substrates and their fluctuations during fasting are relevant to understand the acclimation to fasting. Since fasting is an ecological stressor, we investigated the daily variation of corticosterone levels in feeding and fasting in House Sparrows (Passer domesticus (Linnaeus, 1758)), and its short-term effect on some biochemical parameters. We found daily variations in body mass, glucose, triglycerides, plasma total protein, uric acid, and corticosterone. However, we did not find diurnal variations of hematocrit and the heterophil:lymphocyte ratio (H/L ratio). Moreover, we did not find sex-related differences in any parameter. Throughout fasting, we found variations of glucose, triglycerides, total protein, uric acid, H/L ratio, and corticosterone. During the photophase, biochemical and physiological responses to food deprivation contributed to the efficient use of resources in this small bird. In the course of fasting period, corticosterone could be responsible for alterations of some blood parameters such as glucose.