INTRODUCTION 19 



It is interesting, but perhaps not very productive, to inquire the reasons why Na- 

 ture has deprived the male of his gorgeous feathers during midsummer, for the 

 eclipse of ducks is almost unique in the avian world, most bird families carrying a 

 brilliant plumage throughout the whole summer and not acquiring it again until 

 spring. It is commonly said that the eclipse is a wise provision of Nature to render 

 the male less conspicuous at the time when he is rendered helpless during moult. It 

 is perhaps just as easy to say that the eclipse is merely a periodic repetition of an 

 earlier type of plumage, and the male becomes helpless, shedding his quills, because 

 he gets along very well at this season of profusion without flying about in search of 

 food. However, it seems to me that an entirely different view might be taken, based 

 on the recent castration work of Goodale, Pearl, Boring, and others. We now know 

 that male plumage in birds is not affected by removal of the sex organs, while female 

 plumage is more or less changed to male when ovaries are removed or cease to func- 

 tion through embryonic conditions, old age, or disease. But the power to acquire an 

 eclipse is dependent upon the male sex organs as Goodale showed. Other sex char- 

 acters — spurs, wattles, voice, and behavior — are not so clearly dependent on the 

 secretion of sex glands. It is apparent, then, that the power to produce male plum- 

 age is carried by the female, and that the female sex glands secrete a substance which 

 inhibits or modifies "maleless." Now, we do not have to assume that sex plumage 

 in the male duck is a recent development. On the contrary, it is quite as likely that 

 it is a primitive character and antedates the somber female plumage, and birds like 

 the Florida Duck and the Hawaiian Duck may have arisen from a Mallard-like 

 type through suppression of the male plumage. This throws a very different light 

 on the whole subject. The eclipse may be a recent plumage developed through ne- 

 cessity for protection, while the brilliant winter dress persists at a time of year when 

 it is of little disadvantage, and the birds are well able to look after themselves. In 

 the same way the so-called protective coloring of the female may be recent, in an 

 evolutionary sense, and due to some sort of natural selection, as Wallace long ago 

 pointed out. The eclipse, therefore, may not be a return to a primitive condition at 

 all, but may represent a highly specialized dress. And in this connection we must 

 notice that by nature it is not a return to a female plumage so much as it is to a modi- 

 fied male plumage. I once kept a male Mallard in a cold room all summer, and in this 

 way delayed his moult. When he was brought out into normal surroundings in 

 September, he immediately moulted, but went directly into his full dress, omitting 

 his eclipse. We have then the same anomaly that occurs in castrated ducks — a 

 failure to assume the eclipse. It seems, therefore, that this latter plumage is depend- 

 ent, not only on the presence of the male sex organs, but on their function during 

 the period of breeding activity. A curious anomaly, which I have seen in the Caro- 

 lina Duck is the retention of a perfect eclipse plumage in the male throughout the 

 entire year. 



