146 University of California Publications in Zoology [Vol.12 



tall-stalked milkweed (Asclepias subulata) growing high among the 

 precipitous peaks was also an attraction; so, too, a sage {Hyptis 

 emoryi). The latter was about the only shrub growing on the walls 

 of steep-sided gulches at Riverside Mountain, and here two old nests 

 of the Costa hummingbird were found- on horizontally projecting or 

 drooping branches of the plant. Another nest found March 16 was 

 five feet above the bed of a wash and contained two eggs; on the 19th 

 the eggs were hatched. 



This hummingbird was pre-eminently a desert species ; it was only 

 casually noted even as a forager within the riparian set of associa- 

 tions. It was thus complementary in its local distribution to Archil- 

 ochus alexandri. It was more abundant in the early part of the season 

 than later. This may have been due to local variation in favoring con- 

 ditions as we traversed the region ; or it is quite likely that the males 

 and, as soon as able, the young and females largely departed from the 

 desert floor to seek feeding grounds on the higher desert ranges. 



Besides the localities mentioned above, the Costa hummingbird 

 was noted in Chemehuevis Valley, above Bill Williams River, opposite 

 Cibola, twenty miles above Picaeho, and at Pilot Knob. At the latter 

 point, May 13, full grown juvenals were feeding about flowering 

 ironwoods. 



Seventeen adult specimens of the species were obtained, nos. 12812- 

 12828. 



Tyrannus verticalis Say 

 Western Kingbird 



First seen, two individuals, March 24, at Ehrenberg; next, three 

 individuals, March 29, at the same place; thereafter noted frequently 

 at various points down the river. On the Arizona side five miles above 

 Laguna, where there were many dead cottonwoods, many kingbirds 

 were to be seen in pairs May 25 ; and their behavior led me to suspect 

 them to be about to nest. The same condition held in the river bottom 

 on the California side four miles below Potholes. No actual nests 

 were seen, however. Many individuals believed to be in migration were 

 seen at Pilot Knob, May 12. Seven specimens of this bird were taken, 

 nos. 12829-12835. 



There is also in the Museum a skin (no. 4295) taken by J. G. 

 Cooper at Fort Mohave April 25, 1861. 



