9 C.F.R. § 3.168
(a)
(1) Transportation of all live birds shall be done in a manner that does not cause overheating, excessive cooling, or adverse environmental conditions that could cause discomfort or stress. When climatic or environmental conditions, including temperature, humidity, exposure, ventilation, pressurization, time, or other environmental conditions, or any combination thereof, present a threat to the health or well-being of a live bird, appropriate measures must be taken immediately to alleviate the impact of those conditions. The different climatic and environmental factors prevailing during a journey must be considered when arranging for the transportation of and when transporting live birds. Corrections may include, but would not be limited to:
(b) Birds that are not able to maintain a constant body temperature at ambient temperatures must be transported in a brooder or other temperature-regulating unit that effectively assists the bird in maintaining a constant body temperature during transport.