110 BIRDS OF ILLINOIS. 



SUBFAMILY ANSERINE. THE GEESE. 

 GENUS CHEN BOIE. 



Chen BOIE, Isls, 1822, 563, Type, Anser hyperboreus PALLAS. 

 Exanthemofs ELLIOT, Proc. Phila. Acad. 1868, Type, Anser rossii BAIED. 



Of the three North American species of this genus, two, C. 

 hyperborea, the type, and C. ccerulescens, are precisely alike in 

 the details of form, the only difference being the coloration, 

 which is very distinct in the two; the third species, C. rossii, 

 while agreeing strictly with C. hyperborea in plumage, both in 

 the adult and young stages, differs decidedly in the form of the 

 bill, which is quite peculiar. It seems unnecessary, however, to 

 adopt the generic term Exanthemops, proposed for it by Mr. D. 

 G. Elliot, since the difference in the character of the bill from 

 that of the typical species of the genus is hardly of generic 

 value. The species may be distinguished as follows: 



Synopsis of Species. 



COMMON CHABACTEBS. Adult with whole head and at least part of the neck white (in 

 two of the three species the plumage entirely white, except quills, which are blackish); 

 the bill dull purplish red (in life) with whitish nail, and feet purplish red. Young with 

 head and neck grayish, the rest of the plumage either chiefly grayish brown or else 

 striped with grayish on a whitish ground; bill and feet dusky. 



A. Plumage never chiefly white; the adult mainly grayish brown, with bluish-gray rump 

 and wing-coverts, the head and part of the neck white. Young almost wholly 

 grayish brown, including head and neck. 



1. C. caerulescens. Bill very robust, the posterior lateral outline of the maxilla de- 



cidedly concave; commissure widely gaping, and lower outline of the mandible 

 decidedly convex. (Page 110.) 



B. Plumage of the adult pure white, the primaries black, more grayish toward the base; 



young grayish white, the centres of the feathers darker gray. 



2. C, hyperborea. Bill robust, and shaped like that of C. caerulescena. 



13. C. rossii. Bill small, the posterior lateral outline of the maxilla almost perfectly 

 straight, the tomia closely approximated, and the lower outline of the mandible 

 scarcely convex; in older specimens the base of the maxilla corrugated or warty. 

 Wing. 13.75-15.50 inches; culmen, 1.50-1.70; depth maxilla at base. .85-.9S; tarsus. 

 30-3.00; middle toe. 1.80-2.05. Hab. Northwestern North America.] 



Chen caerulescens (Linn.) 



BLUE-WINGED GOOSE. 



Popular synonyms. Blue Brant; Blue Goose; White-head; White-hea'led Brant, or 

 Goose; Bald Brant;"JBlue Wavey (Hudson Bay). 



Anas caerulescens LINN. 8. N. ed. 10. i. 1758. 124; ed. 12. i, 1766, 198.-GMEL. S. N. i. 1788. 

 513.-LATH, Ind. Orn. ii. 1790, 836. 



