148 



University of California Publications in Zoology [Vol. 12 



breeding birds. I cannot discern in the series as a whole any departure 

 from the characters of M. c. cinerascens of the coast slope of Cali- 

 fornia. The accompanying table shows the size and range of variation 

 in certain respects of the Colorado Valley birds. 



MEASUREMENTS' IN MILLIMETERS OP A SERIES OF MTIAECHUS CINEEASCENS 



CINEBASCENS TAKEN IN THE COLORADO VALLEY FROM NEEDLES TO 



YUMA, FEBRUARY 19 TO MAY 9, 1910 



See text under Molothrus ater obscurus. p. 157. 



The table shows also the decided sexual difference in size in this 

 species, and further that in both sexes there is greater variation in 

 the size and relative narrowness of the bill, than in wing and tail 

 length. Incidentally it would appear that females are subject to 

 greater variation than males. All of the birds whose measurements 

 are presented are comparable as regards stage of plumage wear and 

 age; they are, at youngest, birds of the previous year. 



