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similarity of the sexes, was resolved as soon as I returned to Oxford and was able 

 to consult Dresser's " Birds of Europe." It seems that the male of the first year 

 does not, as a rule, put on the full nuptial plumage, but remains in his juvenile 

 dress of brown and white until after his second spring change of plumage. 

 Dresser also, if I remember right, states that in some cases, even with older birds, 

 the full male plumage is only assumed for a very short time. These statements 

 are confirmed by Macpherson's account of the bird in the book I have already 

 alluded to. Four males were shot for the Carlisle Museum on May 19th, 1884. 

 Two of these were in full black and white. The third was very nearly so, but had 

 the feathers of the crown and nape fringed v^ith brown, but black at the base, 

 which black would in a few days have extended itself over the whole of each 

 feather, for in this case it would seem that the change is not eflFected by a moult, 

 but by an alteration in the tint of each feather. But the fourth bird, which was 

 in full song (alas !) when shot, and was also proved by dissection to be a male, was 

 hardly distinguishable from the female. I had read this account of Mr. 

 Macpherson's before I saw the birds at Wiesbaden, but had quite forgotten it ; 

 and after all, there is a certain pleasure, and also a certain efficacy, in getting well 

 puzzled and then finding out the answer to one's riddle, for which the most 

 patient study of books can never quite be a substitute. 



In these rather rambling personal reminiscences, I think I have in- 

 cidentally mentioned some, at least, of the peculiarities of the Pied Flycatcher ; 

 and I will now only detain you with a few hasty words — first about its eggs, 

 secondly about its relations. 



The nest of this bird is always in a hole or covered place of some kind ; 

 and we should expect it to follow the rule that eggs laid in such places are white 

 or but slightly speckled with some other colour. Anyone who is not aware of the 

 rule may call to mind the white eggs of the Woodpeckers, Wryneck, Kingfisher, 

 Sandmartin, Swift, and many others. When eggs are thus hidden away in holes, 

 they do not need to be protected by assimilating in colour to the grass, foliage, 

 sand, or rock on which they are placed. Why then is it that the eggs of this 

 Flycatcher, instead of being white, are a beautiful pale greenish-blue? I do not 

 think that as yet we know enough about the causes of the colouring of eggs to 

 answer questions like these with much confidence. We may be able to discern a 

 few leading rules, such as the one I have just mentioned, which can hardly as yet 

 be elevated into the dignity of laivs ; but to all such rules there are exceptions of 

 which no convincing explanation seems possible. The only one that occurs to me of 

 the blue eggs in question, is this : — that the blue was adopted at some former period 

 when the bird did not build in holes, and that it still retained it, though i^erhaps 

 fainter than it used to be, under altered conditions. It is certainly a very pale 

 blue, sometimes almost white ; and it may possibly be that, as the coloiir seems 

 to serve no immediate object, it is passing away by imperceptible degrees. But 

 whether this explanation is right or wrong, the matter is worth the attention of 

 anyone who is in the way of meeting with these birds in places where they breed. 

 I must add a very few words, without which this paper would not be complete 

 (though indeed completeness is not my aim to-day), on the kinsfolk of this bird. 



