NO. 12 BODY TEMPERATURE OF BIRDS WETMORE 3 



not all of this labor may gain the stamp of approval from those who 

 may be interested in such lines of research. 



In carrying on these investigations the writer has been indebted to 

 the Smithsonian Institution for a grant of seventy-five dollars from 

 the Hodgkins Fund, for the purchase of specially constructed ther- 

 mometers required, and for certain other minor expenses incurred. 



METHOD OF SECURING AVIAN BODY TEMPERATURES 



In recording the body temperatures of birds it was necessary to 

 work with thermometers that permitted a considerable range in regis- 

 tration as it was found that the degree of bodily heat was high or 

 low according to the species in hand. All records were made in the 

 Fahrenheit scale by means of clinical thermometers similar in form 

 to those used by physicians. For the present investigation it was 

 necessary to have these instruments specially made to give accurate 

 registration ranging from 95°+ to 115° + . Ordinary clinical ther- 

 mometers do not register above iio°+ so that they could not be 

 utilized, for certain passeriform species frequently have temperatures 

 ranging above that figure. 



While engaged in field work these special thermometers were 

 carried constantly in suitable carrying cases. When a bird was shot 

 a temperature reading was taken when the specimen could be reached 

 immediately. If there was delay in retrieving for any reason, an 

 accurate temperature record could not be made, so that it was possible 

 to secure records in less than one-half of the birds that were collected. 

 In taking temperatures of specimens of small or medium size the 

 thermometer was placed in the opened mouth of the bird, and worked 

 down until the lower end was entirely within the cavity of the thorax, 

 usually until it reached the proventriculus. With birds of larger 

 size the reading w^as taken through the anus, with the thermometer 

 thrust in through the cloaca well into the canal of the large intestine. 

 In either case it was necessary to penetrate the body cavity to secure 

 a correct reading. The peripheral circulation of birds is poor, so 

 that often there may be a difiference of two to five degrees between the 

 temperature of the upper part of the oesophagus and that of the body 

 cavity proper. A similar variation was noted between the tempera- 

 ture of the cloaca and the large intestine above it. 



The thermometers used were self-registering, and were so con- 

 structed that they reacted immediately to any increase in heat. The 

 highest point of a reading was reached in a very few seconds, but 

 to insure accuracy the instrument was held in position for a period 



