220 Letters, Extracts, and Notes. [Ibis, 



' Practical Handbook,' that the nestlings have, besides a 

 down directly succeeded by the feathers growing from the 

 same papillae, two other downs which are not succeeded by 

 feathers. But the Hawks have a thick under-down in the 

 feathered state, while the Owls have not, and in the former 

 these nestling-downs which are not succeeded by feathers 

 may be pre-plumulae. I liave^ however, been unable to 

 prove thisj as in no case have I found the nestling-down 

 attached to the under-down of the feathered bird. 



H. F. WiTHEBBY. 



Hampstead, 

 November 1921. 



On a blue-grey example of Egretta garzetta. 



Sir,— In 'A History of Birds/ p. 299, Mr. Pycraft, 

 writing of tlie dimorphism shown by the Reef-Herons, 

 says : — '' It seems highly probable that we have in these 

 instances an illustration of the lines of evolution which 

 will ultimately end in the suppression of the dark and 

 the survival of the white forms. The evolution of the 

 fVhite Egrets has ji^'obably followed precisely similar lines." 

 (Italics mine, A. L. B.) 



In support of the latter theory T should like to place on 

 record that in March 1911, on the Binder River, I met with 

 a blue-grey example of Egretta garzetta. Walking alone 

 ahead of my men and camels I came to a pool in the 

 dried-up river-bed which seemed a suitable place for the 

 midday halt. Here I sat down, concealing myself in the 

 bush on the bank, to watch any wild creatures that might 

 visit the pool until the arrival of ray transport. Almost 

 immediately two birds alighted on the water within 

 twenty yards of me. One was a normal Lesser White 

 Egret, but the other was of a most beautiful clear blue- 

 or lavender-grey throughout. They remained on the pool 

 for some fifteen minutes, during the whole of which time 

 I was examining and comparing them through field-glasses. 



