THE SHELDUCK AND SURFACE-FEEDING DUCKS 213 



scoter the trachea and syrinx are conspicuous for the absence of 

 modifications, but the bronchi are curiously inflated. The velvet and 

 surf scoters show no syringeal peculiarities, but a curious swelling at 

 the upper end of the trachea, and a second in the furcular region. 

 And the precise function of these, as of the syringeal bullse, remains 

 to be demonstrated. 



The surface-feeding Ducks, including the shelduck, display a 

 further peculiarity in the presence of a conspicuous " speculum " on 

 the wing an oblong band, generally of metallic green, formed by 

 the secondary remiges ; and this is commonly bounded by a bar of 

 white or black, or both, formed by the tips of the major coverts. 

 Often a bar along the hinder edge of this speculum is formed by the 

 tips of the secondaries themselves. But there is no need to enlarge 

 upon this feature, since it will be necessary to constantly refer thereto 

 in describing the plumage of the several species, for each has its 

 own fashion in this particular. Let it suffice here to draw special 

 attention to the gadwall, which in this particular differs from all the 

 other surface-feeding species. 



Of the remarkable change of plumage, which annually leaves the 

 male, for a season, in a state of " eclipse," we have already spoken, 

 and the subject will be referred to again in the course of the following 

 pages. 



Similarly, no more than bare mention will be made here of the 

 unusually fleshy and horn-fringed tongues, and the curious armature 

 of the jaws. These are adaptive characters, best dealt with in 

 considering those species wherein they are most conspicuously 

 developed. 



Though monogamous the males display little or no care for their 

 young, this duty being undertaken by the female. She is an assiduous 

 mother, plucking the down from her own breast for the benefit of her 

 incubating eggs, just as the rabbit denudes itself of under-fur for the 

 sake of its newly born young. 



Young ducks, it need hardly be remarked, are nidifugous. But 



VOL. iv. 2 E 



