loS 



backed Shrike in captivit}', contributed to the October 

 (1904) issue of the AviadUiral Magazine, says of the 

 second clutch of eggs laid by this species, (after the 

 first brood had been killed by cold) "they were more 

 brightly ornamented than those of the first clutch, the 

 brown spots near the broad end forming an almost 

 confluent deep-coloured circular head." Has he any 

 theory to account for this; does he attribute it to the 

 more favourable climatic conditions under which the 

 eggs were laid? 



Another point regarding birds' eggs upon which 

 the aviculturist should be able to throw much light is 

 the period of incubation. It is usually assumed that 

 this period is constant for each species. I am inclined 

 to doubt this. It probably varies with the temperature 

 of the air and the closeness with which the bird sits. 

 Some individuals are naturally closer sitters than 

 others. Again the closeness with wliich a bird sits 

 probably varies with the temperature. In India a bird 

 thinks nothing of leaving its eggs for an hour or two 

 on end every day. 



While investigating, last summer, the habits of 

 the Indian Koel (^E7idy7iamis honorata), which is para- 

 sitic on the Indian House-Crow {Corvus splendens) I 

 had occasion to note the incubatory period of Crows' 

 eggs. My method of experimenting was to send a 

 climber up to each nest every morning and have the 

 eggs lowered to me. When a new egg was lowered I 

 marked the date on it and was thus able to ascertain 

 how long it took to hatch out. These experiments 

 showed that there is a good deal of difference in the 

 time of incubation even among eggs in the same 



