8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 'J^ 



was damp and cold so that insectivorous birds were more or less 

 inactive until the sun was well up in the sky. As the air became 

 warmer the birds, correspondingly, became more sprightly. A female 

 magnolia warbler {Dendroica magnolia) secured at 8.30 a. m., had a 

 bodily temperature of 107.0°. At this time birds of similar habit 

 were just commencing to move about and feed. A male of the same 

 species shot at 9.30 a. m. had a temperature of 108.2° and a second 

 male taken at 10.15 a.m. had a temperature of 108.3°. Other war- 

 blers taken between 9.00 a. m. and 10.30 a. m. gave records similar 

 to the last. Thus a female bay-breasted warbler (Dendroica castanca) 

 shot at 9.15 a.m. registered 108.8° and a male killed at 10.00 a.m. 

 registered 108.7°. A male black and white warbler {Mnioiilta varla) 

 secured at 9.15 registered 108.5°. In the observations of this fore- 

 noon it was noted that the red-eyed vireo (Vireosyha olivacea) was 

 astir much earlier in the day than the warblers. This activity appar- 

 ently was reflected in the body temperature as a female taken at 9.15 

 gave a record of 109.7°, a reading distinctly higher than that of the 

 warblers taken at the same time, although average temperatures for 

 the two groups on the whole are about the same. 



In perusal of the data used in preparing this paper many cases are 

 found of range in temperature not correlated with time. These, 

 however, cannot be taken as destroying the value of those instances 

 where early and late readings were available that show a distinct 

 rhythm or increase from early to late. As stated above, the bulk 

 of the records are made during the period of high activity when the 

 bodily temperature approaches a maximum. Range in temperature 

 then is to be attributed to other causes. Had records made early in 

 the morning been available in all of these cases there can be no ques- 

 tion but that an increase in body heat correlated with time would have 

 been shown. 



The daily variation in temperature is much more in bi,rds of small 

 size than in those of greater bulk. Thus Simpson and Galbraith ' 

 found the daily range in the " thrush " (Turdus nierula?) to be from 

 6.8° to 7.5°, in starlings {Stiirnus vulgaris) from 5.2° to 7.2°, while 

 in the domestic fowl it amounted to 1.9° and in the domesticated duck 

 from 1.6° to 1.8°. The marked difference in these cases is noticeable. 



The diurnal variation in temperature that has been noted may be 

 attributed directly to the metabolism of the individual as reflected 

 by its activities. With movement and the digestion of food heat is 

 generated. Although a part of this is dissipated through the usual 



* Journ. of Phys., Vol. XXXIII, 1905, p. 237. 



