300 Phillips, The American Black Ducks. [july 



in a genetic sense. There is certainly evidence of two forms, but 

 unfortunately some of the characters form a graded scale, and are 

 well defined only in male birds, perhaps onl}- in old males. 



There are however, other interesting variations in A. tristis, 

 such as the irregular occurrence of characters that are essentially 

 Mallard. I mean here variations that occur outside of the rather 

 common hybrids with the Mallard. Such variations occur in a 

 large number of full plumaged male birds. I paid some attention 

 to these variations a few years ago and was surprised to find in 

 perhaps 20 to 30 per cent, of male birds taken in late fall in 

 Massachusetts, some of the following abnormalities. One or more 

 brilliant metallic green feathers on the pileum; a general metallic 

 cast to the feathers of the upper parts, especially the rump; the 

 upbending of the central tail feathers, sometimes to quite a marked 

 extent; and the ver}^ much darker appearance of the chest in con- 

 trast to the abdomen, so that a demarcation line was more or less 

 apparent, corresponding to the lower edge of the chestnut in the 

 Mallard. iVlso, as was before noted the posterior end of the 

 speculum may be banded with white, and occasionally both ends 

 are framed by a narrow white band. These characters may 

 appear singly or several of them in combination. 



If they signified a slight infusion of Mallard blood we should 

 certainly expect to find some sort of corresponding variation in 

 the Mallard. Such, however, is not the case. Aside from well 

 marked hybrids, the Mallard presents no evidence of contamina- 

 tion. We must, therefore, regard these variations as slight Mallard 

 tendencies which are being carried along by the species, for the 

 most part in a latent or inhibited condition. 



In examining some pure wild male Black Ducks which I have 

 had in captivity for three years I was much struck with the large 

 amount of green which had appeared in the postocular stripe and 

 along the sides of the pileum. Their rumps were brilliant bronze 

 with iridescent green reflection. There has certainly been a 

 change in these birds in three years, but I have no exact notes. 

 I have never seen so much green in any wild killed Black Ducks 

 as one of these captive ducks shows. 



The occurrence of such variation makes the problem of a possible 

 bi-racial composition of A. tristis even more difficult. I hope to 



