i 914 ] Grinnell: Mammals and Birds of th( Colorado Valley 207 



Colorado River at frequent intervals all along. At Riverside Moun- 

 tain and above Blythe, on the California side, they were still com- 

 mon. A few were noted the first week in April on the California side 

 opposite Cibola. Three individuals were seen on the Arizona side 

 ten miles below Cibola, April 9, and the last for the season were noted 

 April 19, eight miles east of Picacho. Nine specimens of the mocking- 

 bird were secured (nos. 13797-13805), one on this latest day. 



There were no indications, either through dissection or judging 

 from the behavior of the many birds observed, that the species nests 

 in the region. It appears most probable that the species is only a 

 winter visitant from the higher Upper Sonoran Zone to the northward 

 in eastern California and southern Nevada. 



Toxostoma crissale Henry 

 Crissal Thrasher 



A very characteristic element of the fauna of the Colorado bottom 

 along the whole portion of its course explored by us. All evidence 

 shows that it was a permanent resident, and closely restricted at all 

 times to the outermost riparian aasociation, namely the mesquite belt. 

 Wherever this belt was strongly represented, the presence of crissal 

 thrashers was to be recognized through their song or call note. But 

 it was a difficult matter to shoot specimens, as the birds were ever 

 alert, and kept close to or upon the ground beneath dense cover. 

 Locally the thrashers w r ere found foraging among catclaws and iron- 

 woods up desert washes within a mile of the river bottom, and in some 

 places they had temporarily forsaken the mesquites and invaded the 

 willow tracts. The total absence of mesquite in any section of the 

 river valley, however, was a sure indication of the absence of thrashers. 



The species was noted at the following localities: California side 

 five miles below Needles; Arizona side, above Mellen (more numerous 

 than at any other point) ; both sides of the river in the vicinity of 

 The Needles ; Arizona side above Bill Williams River ; California side 

 at Riverside Mountain, above Blythe, opposite Cibola, twenty miles 

 above Picacho, and eight miles east of Picacho ; Arizona side, five 

 miles above Laguna ; and California side in the vicinity of Pilot Knob. 

 Mellen was the only station where definite indications of breeding 

 were found. A female taken February 24 showed conclusively that 

 incubation was in process ; and another contained large ova. Still no 

 young-of-the-year were encountered during the succeeding two and 

 one-half months. 



