AVICULTUBAL EXPERIENCES. 253 



Of the assumption of the breeding plumage by certain birds 

 without a moult, or with only a moult of such feathers as have to 

 be replaced by decorative plumes and crests, I have written 

 recently in the ' Avicultural Magazine,' vol. viii. pp. 132-5 ; 

 therefore, I need not enter into that matter again here. Those 

 interested in the dispute as to the possibility of a change in 

 the colour of feathers can easily refer to this paper, and to one 

 which I published in ' The Ibis ' for 1897. 



It has always seemed to me a strange thing that ornithology, 

 probably the most advanced study in the biological series, should 

 in one respect be at fault, namely, in the reliance which the 

 systematic student places upon the sexing of his specimens by 

 collectors, and his objections to any other method but dissection 

 for ascertaining the sex. Where would the aviculturist be, if 

 (apart from colour differences) he were unable to be sure whether 

 a bird was male or female ? 



In collections one frequently sees skins which have been in- 

 correctly sexed by collectors — the young of Cyanospiza ciris, 

 showing the commencement of the scarlet under surface of the 

 cock bird on the flanks, yet labelled female ; or, perchance, such 

 easily sexed birds as the common Linnet, with no indication as 

 to whether they are males or females. If one points out differ- 

 ences in form of beak, width of skull, length of wing, width of 

 wing-markings, or other (apparently trifling, but actually tren- 

 chant) characters, one is met by the assertion that these are all 

 variable, and therefore unreliable. I discovered a reason for the 

 supposed unreliability of the sexual characters some years since 

 when comparing my male, female, and young of Sialia sialis (the 

 American Blue-bird) with the beautiful series in the British 

 Museum collection. The males of Thrushes are rather longer 

 and more slenderly built birds than the females ; they have 

 narrower skulls, and longer and more slender bills; but, when I 

 compared my young cock Blue-bird (which had acquired its 

 adult plumage) with its parents, I discovered that it was shorter 

 than its mother, had quite as broad a skull, and a distinctly 

 broader and shorter bill. I found that this young bird was 

 uniform in every respect with all males of the same length in the 

 Museum series, and that this apparently variable character was 

 therefore due to the fact that Sialia acquires its adult colouring 



