A HARE'S WHISTLE 313 



that there were also plenty of differences. I have always 

 felt that a good book on the migration of Fishes, both 

 salt-water and fresh, was much wanted. 



A year or two ago a man wrote to me enquiring as 

 you now do about the vent feathers (under tail coverts 

 if you like it better) of the Blackcock. I could only 

 tell him that I knew nothing beyond the fact that they 

 are sometimes marked with black and sometimes not. 

 Never having lived in a Blackcock country my oppor- 

 tunities of observation have been nil y and I could not 

 find out that anybody, here or on the continent, had 

 explained or attempted to account for the variation ; 

 but I remember noticing the fact when a boy, in some 

 Blackgamc sent to my father from Perthshire. 



By way of starting a theory, to be kicked over if 

 need be, I should surmise that the young birds have 

 the bigger marks, the " T " or anchor shape, which 

 gradually lessens to the arrow-head, that to an " ermine " 

 spot and finally disappears. This is just the reverse of 

 the " return marking " on the Wax wing's pinions, for 

 they, I am pretty sure, are only seen in old birds, and 

 they seem to increase with age. 



It would be a very pretty hare for you to start in 

 the " Scottish Annals " : this of Blackcocks' bottoms ! 



A.N. to G. E. H. Barrett-Hamilton : 



February 10, 1905. 



Now I want you to tell me whether you have ever 

 heard, or heard of, a Hare's whistle, if I may so call it. 

 Do you know any one who has described it, and if so 

 who? I believe I have heard it, but very rarely and 

 so long ago that my recollection of it is indistinct. 

 I think it is only uttered at night, and I suppose in 

 the rutting season ; but that I don't know. 



The first time I heard it I had not a notion of what 

 it was, nor did I know for some time what animal it 

 came from, and then, so far as I remember, an old 

 warrener told me. I think the ordinary gamekeeper 



