BIRD BANDING — LINCOLN 343 



his assistants invoked the aid of thermoelectricity. (Cf. Baldwin 

 and Kendeigh, 1927.) A thermocouple, made of copper and con- 

 stantan, was installed in the nest, the thin, flexible wire passing just 

 above the eggs with the junction of the two metals at the middle of 

 the nest. Wires were carried from the thermocouple to a recording 

 potentiometer in the laboratory. Here the recording pen rested 

 on a strip of paper marked in degrees of temperature, and this 

 paper was rolled past the pen at a constant speed. When the female 

 was on the nest the thermocouple came in contact with her body, 

 resulting in an electromotive force sufficient to move the pen in the 

 potentiometer. In fact, so sensitive was this apparatus that a record 

 was made on the moving paper every time the bird stood up and 

 turned around in the nest. 



During the summer of 1926 a record some 250 feet in length was 

 obtained representing 91 days and nights. Four nests of the house 

 wren and one of the robin received similar attention. As would be 

 expected with these species the differentiation between the periods 

 of attentiveness when the bird is actually on its nest, and the periods 

 of inattentiveness, when feeding or resting, is best developed with 

 the female, but nevertheless, the same relation applies also to the 

 male. 



In one case a female wren (71653) was found to incubate during 

 the day for average periods of 14.3 minutes, alternated with 6-min- 

 ute intervals when she was away feeding. During the incubation 

 period she spent every night but one in the nest. On this one occa- 

 sion she left her nest at 8.50 p. m. and did not return until 1.0-1 the 

 next morning. 



One more example, illustrating further the character of the re- 

 searches conducted at the Baldwin laboratory, has to do with the 

 temperature variation in young birds. (Cf. Kendeigh and Baldwin, 

 1928.) Again the house wren was the subject and mercury ther- 

 mometers, and the thermocouple were employed to obtain the neces- 

 sary data. 



Among ornithologists it is now a well-known fact that while the 

 average temperature of adult birds is relatively high there is some 

 variation in this condition. In fact, differences in body temperature 

 of 4° or 5° may occur within a very few minutes. Unusual excite- 

 ment or merely the natural metabolism may be sufficient to effect 

 these variations. The variable temperature of adult birds does not 

 seem, however, to be in any way correlated with atmospheric tem- 

 perature. 



In the case of young birds (that is, nestlings), the situation is 

 different. Their temperature is extremely variable and were they 

 dependent upon their own resources they would be truly " cold- 



