352 OSCAR RIDDLE. 



occurs at night is shown, however, by the facts stated above. 

 Duerden has been urged to obtain this curve from the ostrich. 

 He writes me, however, that in his opinion the extremely nervous 

 ostrich is not well adapted for such experiments. 



Temperature Rhythms in Birds. 



The daily temperature curve of birds was first obtained by 

 Corin and van Beneden. 1 They found that the lowest tempera- 

 ture in pigeons occurs at 4:00 A. M. and the maximum at about 

 4:00 P. M. Their published curve is not altogether convincing 

 because of the single species and few specimens examined, and 

 because the temperatures at the close of their 24 hours' observa- 

 tion were always lower than at the beginning. This undoubt- 

 edly means that the first and highest part of the curve is too 

 high. It was doubtless produced by the fright and struggles of 

 the bird upon the first few insertions of the thermometer into the 

 cloaca. 



The only other observations on the temperature curve of birds 

 which I have been able to find are by Simpson and Galbraith 2 

 who have recently obtained curves similar in most respects to 

 those of Corin and van Beneden, and to those here reported by 

 the writer. The work of these investigators showed, moreover, 

 that in at least one nocturnal bird — the owl — there is a re- 

 versal of the diurnal temperature curve. 



Corin and van Beneden reported that there is a fall in tem- 

 perature from 8:00 A. M. till mid-day. Simpson and Galbraith 

 did not find the same. This and other discrepancies in the 

 results reported, together with the fact that only a few birds had 

 been examined, led the writer to repeat the temperature observa- 

 tions on 16 birds. I, too, fail to find a fall in temperature between 

 8:00 A. M. and noon ; only four showed a fall, nine a rise, and 

 three no change in temperature between these hours. It is quite 

 probable that by taking the temperature of the birds during every 

 hour of the twenty-four, as it was done by Corin and van Bene- 



1 Corin, G., and van Beneden, A., -■" La Regulation de la temperature chez les 

 pigeons," Arch, de Biologie, Vol. VII. , pp. 265-276, 1887. 



2 Simpson, S., and Galbraith, G. G., "An Investigation into the Diurnal Variation 

 of the Body Temperature of Nocturnal and Other Birds, and a Few Mammals," 

 Jour, of Physiol., Vol. XXXIII., December, 1905. 



