178 University of California Publications in Zoology [Vol. 12 



river, although the lines of catclaw or palo verde would seem to offer 

 congenial cover. The Abert townee seems to be closely bound to the 

 vicinity of water, in spite of its evident adaptation in color and 

 structure to a region of desert conditions. 



Although we were camped almost continually within the riparian 

 strip, we saw no evidences of the nesting of this species until April 

 27. on which date near Potholes a half-grown juvenal was found. 

 This, however, appeared to be exceptional, as many adults in pairs 

 were to be seen. A juvenal was taken near Pilot Knob, May 14. 

 where, again, there were no further evidences of nesting. In 1908, 

 Museum collectors found the Abert towhee around the northwest end 

 of Salton Sea, where nests were found plentifully in April ; and in 

 the same locality in 1911. Van Rossem (1911, p. 136) found eggs 

 March 20 and 21. It would appear that the Abert towhee, as in 

 the case of the song sparrow, has along the Colorado River deferred 

 its regular time of nesting until relatively late in the season, so as to 

 avoid the period of rising floods. 



A series of forty -six specimens (nos. 13340-13385) obtained by 

 the present expedition shows striking uniformity in external char- 

 acters; that is, individual variation both in respect to color and size 

 lies within very narrow lmits. Taking a single feature: twenty -two 

 adult males show a wing length of 89.9 to 95.1 millimeters. The 

 average is 92.3, the mid-point of the range is 92.5, and the variation 

 each side of the mid-point is but 2.8 per cent. In twenty-one adult 

 females the average wing length is 86.8 millimeters; the extremes are 

 83.0 and 89.4, the mid-point of the range is 86.2, and the variation 

 on either side of the mid-point is 3.7 per cent. 



Three specimens are in the Museum (nos. 4115—4117) taken by 

 J. G. Cooper at Fort Mohave, February 19 and April 4 and 24, 1861. 



Oreospiza chlorura (Audubon) 



Green-tailed Towhee 



First seen March 14, on the Arizona side above Bill Williams River, 

 one or two individuals; next April 7, on the same side ten miles 

 below Cibola, two seen; then April 15. on the California side twenty 

 miles north of Picacho, several; two were seen April 26 on the 

 Arizona side, five miles north of Laguna; and one, on the California 

 side, Mav 4. five miles northeast of Yuma, and Mav 8 and 10. one 



