Editing Common ostrich (section)

====Breathing adaptations====

The common ostrich has no [[sweat glands]], and under heat stress they rely on panting to reduce their body temperature.<ref name=Schmidt-Nielsen/> [[endotherm|Panting]] increases [[heat transfer|evaporative heat]] (and water) loss from its respiratory surfaces, therefore forcing air and heat removal without the loss of metabolic salts.<ref name=Mitchell /> Panting allows the common ostrich to have a very effective respiratory evaporative water loss (REWL). Heat dissipated by respiratory evaporation increases linearly with ambient temperature, matching the rate of heat production.<ref name=Deeming /> As a result of panting the common ostrich should eventually experience alkalosis.<ref name=zool241 /> However, The CO<sub>2</sub> concentration in the blood does not change when hot ambient temperatures are experienced.<ref name=Schmidt-Nielsen/> This effect is caused by a [[Shunt (medical)|lung surface shunt]].<ref name=Schmidt-Nielsen/> The lung is not completely shunted, allowing enough oxygen to fulfill the bird's [[Metabolism|metabolic]] needs.<ref name=Schmidt-Nielsen/> The common ostrich utilizes [[Gular fluttering#Endothermy|gular fluttering]], rapid rhythmic contraction and relaxation of throat muscles, in a similar way to panting.<ref name=zool241 /> Both these behaviors allow the ostrich to actively increase the rate of evaporative cooling.<ref name=zool241 />
 
In hot temperatures water is lost via respiration.<ref name=zool241 /> Moreover, varying surface temperatures within the respiratory tract contribute differently to overall heat and water loss through panting.<ref name=Schmidt-Nielsen/> The surface temperature of the [[Gular skin|gular area]] is {{cvt|38|C}}, that of the [[Vertebrate trachea|tracheal area]] is between {{cvt|34|and|36|C}}, and that of both anterior and posterior air sacs is {{cvt|38|C}}.<ref name=Schmidt-Nielsen/> The long trachea, being cooler than body temperature, is a site of water evaporation.<ref name=Schmidt-Nielsen/>
 
As ambient air becomes hotter, additional evaporation can take place lower in the trachea making its way to the posterior sacs, shunting the lung surface.<ref name=Schmidt-Nielsen/> The trachea acts as a buffer for evaporation because of the length and the controlled vascularization.<ref name=Schmidt-Nielsen /> The Gular is also heavily vascularized; its purpose is for cooling blood, but also evaporation, as previously stated. Air flowing through the trachea can be either [[Laminar flow|laminar]] or [[Turbulence|turbulent]] depending on the state of the bird.<ref name=zool241 /> When the common ostrich is breathing normally, under no heat stress, air flow is laminar.<ref name=Schmidt-Nielsen/> When the common ostrich is experiencing heat stress from the environment the air flow is considered turbulent.<ref name=Schmidt-Nielsen/> This suggests that laminar air flow causes little to no heat transfer, while under heat stress turbulent airflow can cause maximum heat transfer within the trachea.<ref name=Schmidt-Nielsen/>