1914] Grinnell: Mammals and Birds of the Colorado Valley 179 



each day, near Pilot Knob. In all these eases the birds were in the 

 riparian tract, in willows, arrowweed or quail-brush. Although not 

 numerous, the species is clearly a well-established transient through 

 the region. 



Five specimens secured, nos. 13332-13336, April 7 to 24, show no 

 sign of even a partial prenuptial molt ; if such is actually lacking, 

 the species in this respect resembles Pipilo rather than Zonotrichia, 

 again showing the affinities of Oreospiza to be nearer to the former 

 genus than to the latter. 



Two specimens are in the Museum (nos. 4123, 4124) collected by 

 J. G. Cooper at Fort Mohave, February 13 and March 11, 1861. 



Zamelodia melanocephala melanocephala (Kwainson) 

 Black-headed Grosbeak 



First observed April 12 on the California side twenty miles north 

 of Picacho, one male; next April 25. eight miles east of Picacho. two 

 males; then April 25, five miles north of Laguna, two males. May 4, 

 on the California side five miles northeast of Yuma, many were 

 observed, apparently as a result of arrested migration ; for the pre- 

 vious afternoon and all night, as well as on the day of observation, 

 a strong west wind, laden with dust, was blowing across the desert. 

 The black-headed grosbeaks in company with several other transient 

 species were restlessly foraging through the sheltering willow timber 

 of the river bottom. During the succeeding week, practically until 

 we left the region, the species was numerous. On May 13, especially, 

 another windy day, around the east and north bases of Pilot Knob 

 many black-headed grosbeaks were observed towards evening roving 

 out over the desert in companies, as if preparing for through flight. 



The above observations, in addition to the fact that dissection of 

 specimens taken showed no signs of immediate breeding, leads to the 

 conclusion that the species occurs in the region (inly as a transient. 

 A peculiar thing was the late arrival here, as compared with that on 

 the Pacific slope of southern California ; in fact, the greater part of 

 the migration appeared to take place here in early May, while the 

 black-headed grosbeaks of the other region had arrived a full month 

 previously and in the majority of cases already had nests and eggs. 

 It would appear likely that the grosbeaks passing through the Colo- 

 rado Valley are not bound for the Pacific Coast region, but rather to 



