44 DUCKS, GEESE, AND SWANS 



Distribution. Tropical and subtropical seas, chiefly north of the equa- 

 tor ; north regularly to Florida, Texas, and California, and casually to 

 Wisconsin and Nova Scotia. 



Nest. Made of sticks, placed in the tops of bushes or low trees. 



ORDER ANSERES: LAMELLIROSTRAL 

 SWIMMERS. 



FAMILY ANATID^S : DUCKS, GEESE, AND SWANS. 



KEY TO GENERA. 



1. Tarsus shorter than middle toe without claw. 



?:O 



i 



Fig. 



2. Neck as long as or longer than body . . Olor, p. 70. 

 2'. Neck shorter than body. 



3. Lower mandible without trace of lamellae along sides, 



edges of mandibles strongly toothed or serrate. 

 4. Tooth-like serrations of mandibles sharp and 

 strongly inclined backward 



Merganser, p. 45. 



4'. Tooth-like serrations of mandibles blunt and not 

 distinctly inclined backward 



Lophodytes, p. 47. 

 3'. Lower mandible with a distinct series of lamellae along 



side as well as cutting edge. 



4. Lower part of tarsus with small hexagonal plates 

 and no transverse scutellae in front. 



Dendrocygna, p. 69. 



4'. Lower part of tarsus with a row of transverse scu- 

 tellae across the front. 

 5. Tail without upper coverts, the base of the stiff 



feathers scarcely concealed. 



6. Tail feathers 18 ... Erismatura, p. 64. 



6'. Tail feathers 20 ... Nomonyx, p. 65. 



5'. Tail with base well concealed by upper coverts. 



6. Hind toe without a flattened membraneous 



lobe. 



7. Bill long and much wider near end than 

 toward base .... Spatula, p. 54. 

 7'. Bill not much wider near end than at base. 

 8. Tail feathers wide and rounded at end. 



Aix, p. 55. 



8'. Tail feathers narrow and pointed at tips. 

 9. Tail graduated more than a third of its 



total length. 



10. Tail feathers 14 . Mareca, p. 49. 

 10'. Tail feathers 16. 



11. Bill longer than middle toe with- 

 out claw . . . Dafila, p. 54. 

 11'. Bill shorter than middle toe with- 

 out claw 



Chaulelasmus, p. 49. 

 9'. Tail graduated less than a third of its 

 total length. 



