The development of effective homeothermy and endothermy by nestling starlings

Abstract

1. 1. Loss of body temperature and metabolism were measured in nestling European Starlings ( Sturnus vulgaris L.) for brood sizes of 1, 3, 5 and 7 at four air temperature ranges. Data were collected for age classes 1–6, 9, 12, 15 and 18 days. 2. 2. A distinction is made between effective homeothermy and effective endothermy as determined for broods under semi-natural conditions vs homeothermy and endothermy determined for isolated chicks. 3. 3. Endothermy developed slowly. Shivering thermogenesis began at about 6 days; peak metabolism was not reached until about 10–12 days. Analysis of variance indicated that brood size, air temperature, age, and all two-way interactions were significant. 4. 4. Homeothermy was achieved earlier than endothermy in chicks for all brood sizes under all test conditions. For a given air temperature effective homeothermy was achieved earlier by individuals within larger broods. This was primarily due to inertial effects retarding heat loss. 5. 5. The homeothermic status of broods of various sizes can be predicted from metabolic abilities of individuals within nests.