Thermoregulation During Flight
Flight is the most energy consuming process, in the progress of which the basal metabolic rate increases in a multitude fashion in comparison with resting state and hence results in ample amount of heat generation.
All possibilities are there for development of hyperthermia in birds during flight. This sort of flight induced heat load, triggers responses in birds to have increased the evaporative water loss and converted heat loss from unfeathered areas of the bird to the environment. Flight instigated hyperthermia is beneficial for improving the thermal gradient between the birds and the environment and hence for heat dissipation to the environment. Another important function of hyperthermia during flight is that it serves as mechanism of heat storage. Bird can get rid of this heat storage during flight in later periods. It is established that in flying birds, core temperature is independent of the ambient temperature. The degree of elevation of core temperature is independent of ambient temperature but is positively correlated with the rate of flight. Flight induced hyperthermia is not the result of inadequacy in thermoregulatory mechanism but it is an adaptive response to flight, a strenuous exercise. The thermal resistance caused by skin and the feathers could possibly give an explanation for paradoxical increase in skin temperature of flying birds.This is also an adaptive response against an inevitable rise in heat flow.
Leg trailing is the behavioural method of thermoregulation exhibited by most of the birds during flight. The unfeathered portions of bird’s legs play an important role in non-evaporative cooling (radiation and convection) during flight. Hovering mode of flight is also exhibited by some species of birds, which will increase the air flow and helps in heat dissipation during flight.
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