1914] Grinnell: Mammals and Birds of the Colorado Valley 169 



To enumerate localities of occurrence would be to list every place 

 explored along down the river to the collecting station on the Arizona 

 side five miles north of Laguna. By the time we reached this point, 

 April 21, intermediate sparrows had become notably fewer in numbers 

 than immediately before. Still there were several to be seen each day 

 in the arrowweed and willow thickets until the 26th of April, when the 

 last for the season were seen at the same place, and one, a female, 

 taken. 



There is in the Museum a skin (no. 4177) taken by J. G. Cooper 

 at Fort Mohave, January 26, 1861. 



Of thirty individual specimens shot before the completion of the 

 prenuptial molt, April 15, fifteen are in the brown-and-gray-crowned 

 first winter plumage. As there was, as far as I know, no intention 

 of selecting adults in preference to immatures, these figures probably 

 give an approximate proportion of birds-of-the-year at that season 

 (February 15 to April 15) that is, fifty per cent. 



The whole series taken, thirty-four specimens (nos. 13136-13169), 

 serves well to indicate the period occupied in the prenuptial molt. The 

 earliest individual showing molt, adult female, March 27 (no. 13160), 

 shows many new feathers unsheathing in the mid-dorsal and pectoral 

 tracts. An immature of the same date (male, no. 13161) shows a few 

 unsheathing feathers in the mid-dorsal region only. An adult male, 

 April 6 (no. 13162), is well along tow T ard completion of the molt, 

 though many old feathers persist in the capital region. It is of course 

 to be remembered that the prenuptial molt does not involve any of the 

 flight feathers, or, in this species, the wing and tail coverts. 



That the molt program is not exactly simultaneous in all indiv- 

 iduals is shown by an adult female (no. 13163) taken April 7, in which 

 no sign of molt is apparent. An immature (male, no. 13165), April 

 10, is in the midst of the molt all over the body. In another specimen 

 (female, no. 13166), April 18, of age not with certainty recognized, 

 the molt is approaching completion. In the remaining three specimens, 

 females, April 20, 24, and 26, feather growth in all the tracts involved 

 is evidently complete, though in each individual a few old abraded 

 feathers still remain in the post-auricular and pectoral regions. 



It would thus appear that the spring molt occupies a period of not 

 to exceed twenty-five days. Because of lack of uniformity in date of 

 inception in different individuals or rate of the process, this is prob- 

 ably somewhat more than the time occupied in any one individual. 

 The nuptial dress differs in color from the adult winter plumage in 



