User:Saucyluffy/Great tit

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Great tits have been found to possess special physiological adaptations for cold environments. When preparing for winter months, the great tit can increase how thermogenic (heat producing) its blood is. The mechanism for this adaptation is a seasonal increase in mitochondrial volume and mitochondrial respiration in red blood cells and increased uncoupling of the electron transport from ATP production. As a result, the energy that would have been used to make ATP is released as heat and their blood becomes more thermogenic. In the face of winter food shortages, the great tit has also shown a type of peripheral vasoconstriction (constriction of blood vessels) to reduce heat loss and cold injury. Reduced cold injury and heat loss is mediated by the great tits’ counter-current vascular arrangements, and peripheral vasoconstriction in major vessels in and around the birds’ bill and legs. This mechanism allows uninsulated regions (i.e., bill and legs) to remain close to the surrounding temperature. In response to food restriction, the great tits’ bill temperature dropped, and once food availably was increased, bill temperatures gradually returned to normal. Vasoconstriction of blood vessels in the bill not only serves as an energy saving mechanism, but also reduces the amount of heat transferred from core body tissues to the skin (via cutaneous vasodilation), which, in turn, reduces heat loss rate by lowering skin temperature relative to the environment.