214 University of California Publications in Zoology [Vol. 12 



There is also in the Museum collection a skin (no. 4216) taken by 

 J. G. Cooper at Fort Mohave, March 26, 1861. 



The spring molt (which involves only the body plumage) is well 

 along in the bird (a male) of the latter date and in birds of April 4, 

 5 and 6 appears to be nearly or quite complete. In the females of 

 these dates there is, however, a want of clearness and continuity in 

 the gray of the dorsum and pileum. and upon close examination this 

 is found to be due to an interrupted and irregular replacement of 

 feathers. This results in a mixture of new clear gray feathers and 

 worn ashy ones. 



Of the April birds there are six females and one male. The latter 

 (no. 13882), in comparison with series of Polioptila caerulea obscura 

 from western California, has an extraordinary amount of black on 

 the forehead, there being a frontal band of an approximate width of 

 live millimeters, with a conspicuous extension posteriorly over each 

 eye. Moreover, two of the females (nos. 13880, 13881) show a distinct 

 supra-loral black line on each side, the two lines converging and 

 meeting over the base of the culmen. This tendency to blackness on 

 the crown may characterize a race wintering in the Colorado Valley 

 and breeding in the Upper Sonoran zone of desert mountains to the 

 northwestward. Material is not at hand to permit following up the 

 matter. 



Polioptila plumbea (Baird) 

 Plumbeous Gnatcatcher 



A common resident along the whole line of exploration from Needles 

 to the Mexican line. The series of thirty-five specimens secured (nos. 

 13887-13921) represents the following localities: California side, at 

 Needles and five miles below Needles ; Arizona side, above Mellen and 

 at the foot of The Needles; California side in Chemehuevis "Valley, 

 at Riverside Mountain and above Blythe; Arizona side, at Ehren- 

 berg; California side, opposite Cibola, twenty miles above Picacho, 

 eight miles east of Picacho, and near Pilot Knob. 



There are also in the Museum two skins (nos. 4219, 4220 I taken by 

 J. G. Cooper at Fort Mohave, February 19 and March 19. 1861. 



The desert wash association, with its catclaw, palo verde, ironwood 

 and smaller woody and stiff -twigged plants, was the preferred habitat 

 of this bird, though it occurred also in the Atriplex and mesquite belts 

 along the river, even straying occasionally into the arrowweeds and 



