186 University of California Publications in Zoology [Vol. 12 



larly at Ehrenberg, March 26 and 28 ; two seen opposite Cibola, April 

 5 ; and a few ten miles south of Cibola, April 8. One specimen taken, 

 no. 13395. The species occurs in the region as a transient only. 



Stelgidopteryx serripennis (Audubon) 

 Rough-winged Swallow 



First noted February 20, three individuals, five miles below Needles 

 on the California side; next noted at Mellen, Arizona, February 23, 

 thenceforth observed daily and at every station all the way down 

 the river to Pilot Knob. This swallow forages alike over the river 

 and flood-plain, and out over the desert where I saw it as far as I 

 went (opposite Cibola fully six miles from the river). At Ehrenberg, 

 March 24 to 29, many rough-winged swallows were to be seen close 

 about the old adobe houses. They roosted by the half-dozen on wires 

 stretched overhead for drying meat. Rafter holes in the walls, up 

 under the thatches of those houses still possessing roofs, would appear 

 to offer attractive nesting sites for these swallows. Individuals were 

 seen flying up to such openings, though actual nest-building had not 

 yet commenced. 



Back in the hills, two to five miles west of the river and twenty 

 miles north of Picacho, one or two pairs were noted in nearly every 

 ravine. April 16 a nesting site was located in a naturally eroded hole 

 in the face of a conglomerate wall. The cavity was too deep and 

 too small to investigate. But the actions of the birds plainly indicated 

 that it held either eggs or young. 



At a number of places below Picacho, and down to Pilot Knob, 

 nesting holes of rough-winged swallows were observed in hanks, but 

 always above flood level. In no case did we see birds attempting to 

 nest in banks subject to undercutting or overflow, although these would 

 appear to be in some cases otherwise quite suitable, suggesting extra- 

 ordinary powers of anticipatory "discrimination" on the part of the 

 birds. Near Pilot Knob, May 14, a nest burrow was found in the 

 wall of a wash meeting the river at right angles, and only some fifty 

 feet from the brink of the main bank. This burrow was about eight 

 feet above the floor of the wash ; the terminal cavity was found to 

 contain one fresh egg. Twenty-six specimens of this swallow were 

 secured, nos. 13452-13477. 



