NORTHERN YELLOW-THROAT 251 



Nest. — Minot 1 describes the nest as recalling a coarse type of 

 Chestnut-sided Warbler architecture. Nests in the Crandall collection 

 from Colorado are composed of grasses and rootlets lined with hair; 

 while a nest from California is described as small and loosely made, 

 composed of grasses, principally 'wild oats,' lined with fine grasses and 

 a little hair. 



Eggs. — 3 to s, usually 4, very rarely 5. Ground color white to 

 slightly creamy, marked with many shades of brown, dark lilac, rufous, 

 purplish black and numerous under shell spots of lavender ; these mark- 

 ings occur in the form of specks, spots, blotches, in some cases much 

 run together, and irregular lines, heavier at the larger end where they 

 often form an indistinct wreath; in many types the smaller half of 

 the egg is almost devoid of markings. Size; average, .71X.52; 

 extremes measure .oox.50 and .77X.56. (Figs. 104-106.) 



Nesting Dates. — Estes Park, Colo., June 15 (C. W. C.) ; Sonoma, 

 Calif., May 2 (C. W. C.) ; Tacoma, Wash., June 11-18 (Bowles). 

 Biographical References 



(1) H. D. Minot, Notes on Colorado Birds, Bull. Nutt. Orn. Club, V, 

 1880, 227. 



Genus GEOTHLYPIS Cabanis 



Geothlypis is characterized chiefly by its short wing and rounded 

 tail. The wing in our species is never more than .25 inches longer than 

 the tail and sometimes equals it in length, and averages only two and 

 three-fourths times as long as the tarsus ; the outer primary is always 

 shorter than the second and the outer tail-feather is about .25 inches 

 shorter than the longest ; the tarsus is longer than middle-toe and nail, 

 the hind-toe not so long as its nail. 



As here restricted, Geothlypis contains about twelve species, only 

 two of which are North American, while one is Bahaman and the 

 others range southward through Mexico to Argentina. 



The species of Geothlypis appear to respond to the influences of 

 their environment more readily than do other North American War- 

 blers. Seven forms of the Bahaman bird are recognized and of our 

 G. trichas an equal number are current. In several instances, however, 

 the great individual variation which characterizes these birds, so 

 obscures their subspecific differences that identification is often attended 

 with much uncertainty. 



Northern Yellow-throat 



GEOTHLYPIS TRICHAS BRACHIDACTYLA (Swains.) Plate XX 



Distinguishing Characters. — This species and its several races may always be 

 distinguished from other North American Warblers by the characters given 



