1914] Ghinnell: Mammals and Birds of the Colorado Valley 185 



work. He had tried to drive them away repeatedly in previous years 

 by destroying their nests. But the birds persisted in returning. Last 

 year he had procured a quantity of poisoned wheat and spread it out 

 on nearby ground, without, however, bringing any perceptible results! 

 Our nineteen specimens, nos. 13396-13-414, show slight peculiarities 

 as compared with examples from central California and Illinois. They 

 are smaller: wing 100.0 to 108.0, averaging 103.2 mm. (see Ridgway, 

 lf>04, p. 48) ; the frontal light patch is cinnamon instead of whitish; 

 the feathers of the dorsum are more conspicuously edged with clear 

 white; the belly is whiter. These differences are indicative of the 

 probable fact that the cliff swallows of the lower Colorado Valley are 

 near in derivation to the forms in Mexico, particularly Petrochelidon 

 lunifrons tachina Oberholser. which is recorded north on the east side 

 of the Mexican plateau to southern Texas. 



Hirundo erythrogastra Boddaert 



Barn Swallow 



Observed but once: one, evidently a migrant, flying overhead at 

 Potholes, April 29. 



Iridoprocne bicolor (Vieillot) 



Tree Swallow 



Recognized but once: March 23 a small number were noted flying 

 back and forth over the second bottom on the California side at our 

 collecting station above Blythe. One specimen taken, no. 13394. Evi- 

 dently only a transient through the region. 



Tachycineta thalassina lepida Mearns 



Northern Violet-green Swallow 



First noted March 4 opposite The Needles. No birds were actually 

 seen; but a tumult of the characteristic twitterings high overhead 

 belonged unmistakably to this swallow. The sky was dazzlingly bright 

 so that small objects at but a moderate distance were invisible. Next 

 seen with certainty, ten or so, on the Arizona side, March 7; then 

 above Bill Williams, March 13. A few violet-green swallows were 

 seen above Blythe March 23, in company with other swallows; simi- 



