DUCKS. 



147 



are then connected by horizontal tunnels, and finally with the common entrance. Each 

 breeding chamber is closed above with a tightly-fitting jiiece of sod, which can be 

 lifted up like a lid, when the nest is to be examined and plundered. Such a complex 

 burrow may contain from ten to twenty nest-chambers, but in the latter case there 

 are usually two entrances. The birds, which, on account of the protection cvtended to 

 them through ages, are quite tame, take very eagerly to the burrows. As soon as the 

 female has laid six eggs the egging commences, and every one above that number is 

 taken away, a single bird often laying twenty or thirty eggs in a season. The birds 

 are so tame, that, when the lid is opened, the female still sits on the nest, not walking 

 off into the next room until touched by the egg-gatherer's hand. When no more 

 fresh eggs are found in the nest, tlie down composing tlie latter is also collected, being 

 in quality nearly equal to eider down. 



/Vh ~~~- 4ii*^ rn ^V'U^ • 



Fio. 70. — Tadonia Indoma, slieldrake. 



The coscoroba duck {Voscoroba coscoroba), is a South American form which, on 

 account of its large size, graceful neck, and white color is usually referred to the swans. 

 It is a true duck, however, as proven both by external and internal characters. 



Tiie true and typical ducks (Anatina'), the central and most ninnerous group of 

 the family, are conventionally divided into two smaller divisions, according to the 

 presence or absence of .1 membranaceous lobe to the hind toe, but while there gener- 

 ally is an easily ap]ireciable difference between a river-duck and a sea-duck, several 

 forms are so completely intcnnediate that it is nearly impossible to decide to which 

 category they should be referred. As far as we know, there is no character, external 

 or internal, that will naturally divide the sub-family in two. As to the value of the 

 formation of tlu' traclica and its labryinth, we have already sjioken above. The sub- 

 family is a tolerably homogeneous one, and only few outlying forms belong to it. 



