1914] Grinnell: Mammals and Birds of the Colorado Valley 161 



There is in the Museum an adult male (no. 4346) taken by J. G. 

 Cooper at Fort Mohave March 31, 1861; and another skin (no. 5959) 

 taken by W. W. Holder at "Mineral City" (=Ehrenberg) March 8, 

 1864. The species is probably a regular winter visitant to the Colo- 

 rado Valley. 



Agelaius phoeniceus sonoriensis Ridgway 

 Sonora Red-winged Blackbird 



First seen March 6, when a large flock was encountered flying north 

 along the Arizona shore at the foot of The Needles. Next noted at 

 Ehrenberg. Arizona, during the week beginning March 24. Here not 

 more than fifteen individuals all told were staying close about the town, 

 associated with the cowbirds and Brewer blackbirds which foraged in 

 the cattle corrals. On the same side of the river, ten miles below Cibola. 

 April 7, four individuals were seen in flight up the river. Several 

 small flocks came to notice at our station on the California side eiu'ht 

 miles east of Picacho. April 18 to 20. On both sides of the river 

 above Laguna and at Potholes. April 22 to 29, many were seen, mostly 

 in pairs or small flocks pursuing their way up the river. It was 

 observed in nearly every instance that these presumably migrating 

 birds, instead of taking a more direct route northward up the valley, 

 closely followed the river bank even when through the meandering of 

 the stream this course was sinuous in the extreme. 



At Potholes and below, evidence was unmistakable that red-wings 

 were preparing to nest, though no nests had been built as yet up to 

 the time of our examination. At one place in particular, on the 

 California side of the river, about five miles northeast of Yuma, a 

 large colony had evidently settled for breeding purposes. Here in 

 the late afternoon of May 2, on the inside of a large bend of the river, 

 we were afforded opportunity of securing a good series of specimens 

 and of observing the behavior of the birds. The males were by them- 

 selves, spaced out, and perched at the tips of willow saplings in an 

 extensive dense tract of these on ground which at a little higher stage 

 of the rapidly rising river would have been wholly inundated. The 

 male birds were singing continually, and displaying themselves con- 

 spicuously in short circling flights, but each one behaving independ- 

 ently of any other. The females on the other hand were quietly for- 

 aging on the ground in close flocks in a much younger growth of 



