Abstract
Animals initiate physiological mechanisms to re-establish homeostasis following environmental stress. To understand how bird physiology responds to abiotic stress, we quantified changes in haematological markers of chronic stress response and body condition of male zebra finches (Taeniopygia guttata) acclimated for 18 weeks to hot and cool temperatures (daytime temperature: 40°C and 23°C) with water available ad libitum or restricted during half of the active phase. Ambient temperature induced greater chronic stress than restricted water availability. While cool compared with hot temperatures induced higher numbers of heterophils and heterophil to lymphocyte (H:L) ratios and reduced total leucocyte count, water restriction decreased the number of lymphocytes compared with water ad libitum. Body condition correlated with haematological parameters showing that birds with better condition had greater capacity to face environmental stress. Therefore, prolonged exposure to cool periods may result in chronic stress in zebra finches, especially if body condition is weakened.