occupied by Bii^ds in Incubation. 53 



poultry-rearers, I made the preliminary experiments at an 

 average temperature of about 105° Fahr. ; but believing 

 this to be on the high side as regards the majority of our 

 native birds, I reduced it in 1888 to 104°, and in 1889 still 

 further to 102°"5, in consequence of temperatures obtained 

 by placing a small thermometer under a Domestic Hen, a 

 Dove, and a Redpoll. The first two were sitting on eggs 

 and gave 102° and 101°-5 to 102° respectively. The Redpoll 

 was placed on the thermometer lying on a sheet of cotton, 

 and held there for fully twenty minutes, with the result that 

 the mercury rapidly rose to 103°* 75, but soon fell again to 

 103°, at which it remained steady during the last ten minutes. 

 In this connection the following statement by M. Georges 

 Claraz (P. Z. S. 1885, p. 325) will be read with interest:— 

 " Pour la Rhea americana .... la temperature necessaire est 

 de 103° Fahr.-" Again, Mosenthal and Harting, in their 

 book on ' Ostriches and Ostrich Farming,^ say (p. 217) 

 " 104° is the natural heat of the Ostrich mother,^^ and recom- 

 mend for the artificial hatching of Ostrich eggs '^ 102° Fahr. 

 when first put in, to be gradually reduced to 100° at the end 

 of two weeks, then in two weeks more to 98°.'"' The temj>e- 

 rature in the mound of a' British Turkey has been stated at 

 89°^. 



The eggs in the incubator were looked at and turned twice 

 a day^ — morning and evening — and the drawer left open from 

 15 to 20 minutes on each occasion. 



From the outset it was evident that either several incu- 

 bators would have to be used, or some other method of observa- 

 tion employed in conjunction with that already in use, if sub- 

 stantial results were to be obtained within a reasonable time. 

 The only other courses were to watch the nests while the 

 parents themselves incubated the eggs, or to place the eggs 

 under domestic birds — Hen, Dove, or Canary, for instance, 

 according to size. For several reasons I thought it better to 

 avail myself, as far as possible, of both of these additional 

 methods rather than to use more incubators. For valuable 

 co-operation in watching nests of the Passeres, I am greatly 

 indebted to my friend Mr. Bruce Campbell. 

 * Cassell's Birds, iii. p. 271., 



