14G NATL UAL UISTOllY OF BIRDS. 



witJi a fenestrated or closed labyrinth renders the character useless as such. As ex- 

 aiii|ilc'S may be (juoted the common cider, which has a labyrinth much like that of the 

 mallard, while it is fenestrated in Surhidiornis and lihodimtssa. Some sjiccics have, 

 in addition to the labyrinth, or alone, a bulbous cx|iansion hiirhcr uji on the trachea, 

 as in the rosv-billcd duck {^Metopiana pejwsaca) from South America, without lobe to 

 the hind-toe, and in the vclvet-scolor ((.Hdetnia fused), one of our common sea-ducks. 



"We shall now briefly review the minor i^roujis into which this sub-family is divis- 

 ible, commencing with the trcc-tlucks, which seem t<> be somewhat isolated, and, 

 j)erhajis, mii^ht have been made to form a separate sulvfamily in connection with the 

 Muscifvy duck and the gcnns Surkidiomiit. The tree-ducks (J)eii<7rori/f/iHi) are 

 remarkable for th<'ir lonp thin neck, the lonj; hind-toe, their arboreal habits, and their 

 curious geograjihical distribution. The genus consists of about a dozen forms, which 

 inhabit the tropical regions of the earth, chiefly America and the Malayan archipelago, 

 but also India, Madagascar, Africa, and Australia. This general distribution is not 

 80 strange, since wc have numerous parallels, as repeatedly observed on previous pages. 

 But in this case we arc confronted with the fact that one species, D. vidiiata, occurs 

 both in Africa and in South America. Dr. Sdater, however, thinks it jtrobable that 

 it has been introduced to the latter country by negro slaves, but we are not aware that 

 this is more than a mere guess. The Muscovy duck {('airina niosc/uita), originally 

 neotropical, but now domesticated nearly all over the earth, is too well known to 

 detain us further, and the 'black-backe<l geese' {Sarkidiortiis) need only be men- 

 tioned for the carious, compresseil, high wattle, that surmounts the culmen for nearly 

 the whole of its length. The three species, one of which is found in South America, 

 one in South Africa and Madagascar, and one in India, are exceeilingly alike, ami 

 were once thought to be only one species, making one more instance of the kind of 

 geograj)hical distribution alluded to above. 



Xot very distantly related to the foregoing genera arc the true sheldrakes, Tadorna, 

 of which the typical species ( T. tadorna) is well worth mentioning. Considering its 

 striking coloration, the head and neck being greenish l)lack ; anterior part of back, 

 sides, and breast rusty brown, shouldci-s and middle of under j)arts black ; wing- 

 speculum green, rusty brown behind; bill and frontal knob bright carmine, legs flesh- 

 color, it will be (perceived that it is one of the most striking-looking ducks. The size 

 is that of a mallard, but it stands higher on the logs, and looks much statelier and 

 walks better, on account of the more central ]>osition of the feet. The sheldrake 

 inhabits the coast of temperate Europe, and is also found in corres]H>ndinii: latitu<les on 

 the eastern shores of the I'ahearctic continent. It is .sedentary, and, in spite of its 

 unlobed hind toe, is strictly confined to salt water. The jilum.age is only molted once 

 a year ; there are no seasonal changes, and both sexes are nearly alike in coloration. 

 Its breeding history is most interesting, for it nests in bm-rows made in the .sand-dunes 

 of the coast, either made by themselves or other burrowing animals, as rabbits or foxes. 



The inhabitants on several of the small sandy islands off the western coast of .Tutland 



not.ably the island of Sylt — have made the whole colony of sheldrakes breeding there a 

 source of consiilerable income, by juiliciously taxing the birds for Ci^gs and down, 

 su])plying them, in return, with burrows of easy .access, and i)rolecting them against all 

 kin<ls of injury. The construction of such a duck-burrow is described by Johami 

 Friedrich Naumann, who says that all the digiriiig, with tlie exception of the entrance- 

 tunnel, is made from mIiovc. On top of a small, rounded hill covered with grass, the 

 breeding chambers .are first dug out to a uniform depth of two to three feet. These 



