Acquisition of Homeothermy in the Black-eared Kite, Milvus migrans lineatus

Abstract

The development of homeothermy was investigated in a hand-reared black-eared kite, Milvus migrans lineatus. The 20-day-old nestling was capable of thermoregulating at about 95% of the adult ability at the ambient temperature of 20℃. In effect, the kite which is one of large altricial birds acquires the homeothermy in an earlier growth stage than do small altricial ones, Such precocious development of homeothermy in the kite appears to be caused by the large body mass resulting in decreased surface to volume ratio and in increased heat production, and it allows the parents to increase the foraging time early in the nestling period. In other words, the precocious development of homeothermy plays an important part in the growth and survival of the kite nestling which requires more food and energy than do the nestlings of small altricial birds