Lesser Nighthawk (Chordeiles acutipennis) dissipating heat through thermoregulation. Ambient temperature of 40° degrees. - 4K Bildbanksvideo

Measures 19 to 24 cm in length. The male has a white throat and a white bar at the end of the tail, while the female has a yellowish throat and does not have the white stripe on the tail. In the case of the gullar flutter mechanism, this consists of the bird rapidly vibrating the hyoid bone, most of the time asynchronously with breathing. It has advantages over panting, as it is efficient in losing evaporative heat, since the oral surface and vascularization are intense, in addition to not intensely increasing the metabolic rate. In this context, species that predominantly use gullar flutter or skin evaporation to lose heat, such as caprimulgiformes, have the most efficient evaporative cooling because the ratio between evaporative heat loss and metabolic rate is higher than that of those who perform panting, in addition to having little or no metabolic cost.