Egg Temperatures of Wild Birds Under Natural Conditions

Abstract

A number of incidental observations on the temperature of birds' eggs during incubation can be found in the literature but no detailed study of the problem has been made. The purpose of this investigation is to determine the actual egg temperatures with some of the factors involved for many of the species and orders of birds available in the Cleveland area. Murray ('26), Baerenprung ('51), Eycleshymer ('07), Covalt ('12), Cadman ('23) and Philips and Brooks ('23) determined by means of thermometers the egg temperatures under the incubating hen. Their results indicate that the temperature of the hen's egg is from 37.8 to 39.40 C. Moran ('25) in his studies on the hen's egg used thermocouples. Baldwin and Kendeigh ('32) were the first to use thermocouples to determine the egg temperatures in wild birds. For house wren eggs they found a fluctuation between the average limits of 34.0 and 37.00 C. Wetmore ('33) discussing the work of Baldwin and Kendeigh gives the egg temperature of the house wren between 38.9 and 41.10 C. Wetmore evidently confused the body temperature with the egg temperature. A few determinations of the mound temperature of the Megapodes has been made by the use of thermometers. In this particular case the temperature of the part of the mound in which the eggs are found probably represents closely the egg temperature. The. temperature was found to be between 32.2 and 33.9? C. The bird appears to control the temperature of the mound by adding or removing organic material (Seth Smith '30, Meyer '30, and Wetmore '33).