58 PROCEEDINGS OF THE ACADEMY OF 



with great numbers of these birds ; except along the valley of the Colorado 

 Chiquito River, where there were no suitable places for their habitation. It 

 is preeminently a saxicoliue species, and always found congregated in con- 

 siderable, sometimes in immense numbers, in the vicin ty of huge cliffs and 

 piles of rocks ; usually associating intimately and peacefully with several spe- 

 cies of Hirundmidce, especially Hirundo lunifrons. Its flight is very rapid and 

 vigorous ; similar in character to that of the common Chmtura. Its note is an 

 often and quickly repeated twitter, loud and shrill, quite different intone from 

 that of Chce.lv.ra pelasgia. It builds upon the vertical faces of precipitous 

 rocks. 



Notwithstanding the identity of Baird's with Woodhouse's species, I do not 

 think that the former's name, accompanied by a definite description, should 

 give way to the brief and incorrect indication of Acanthylis saxutilis. 



CAPRIMULGIDJE. 



53. Antrostomus Nuttalli (Aud.) Cassin. 



This widely distributed species, which extends from Missouri and Kansas to 

 the Pacific and south into Mexico, is particularly abundant throughout Ari- 

 zona. At Fort Whipple it is a summer resident, arriving late in April and 

 remaining until October. So numerous is it in some localities that around 

 the camp-fires of the traveller a perfect chorus of their plaintive two-s.\llabled 

 notes is continued all through the night, and some of the performers are usually 

 so near that the sharp click of their mandibles which follows each cry is distinct- 

 ly audible. But from the difficulty of observing them, little of their personal 

 habits, beyond their cries, are known to us. I never saw a single bird in Ari- 

 zona, though I have listened to perhaps many hundred. Their dissyllabic note 

 is a peculiarity which well distinguishes them from A. vociftrus. 



I have been informed that the trissyllabic notes of A. vociferus have been 

 heard in Arizona; but I consider the statement as very improbable. 



(54.) Chordeiles Henryi Cass. 



Abundant throughout the Territory. At Fort Whipple a summer resident, 

 arriving in April and remaining until October. It is particularly numerous in 

 August and September. 



This species, if it be really one, is not larger than C. popetue, and it otherwise 

 is so closely allied to the latter, as to render the separation of some specimens 

 a matter based upon locality rather than upon differences to be found on com- 

 parison of skins. The western bird presents variations quite parallel with 

 those of popetue ; but nevertheless the average is much lighter colored and 

 with more rufous about it, than usually exhibited by eastern specimens. 

 These remarks are founded upon examination of very extensive series of both 

 birds which have been at my disposal. 



(55.) Chordeiles Texensis Lawr. 



Common in the Colorado valley to even further north than the latitude of 

 Fort Whipple ; but not observed elsewhere further north than some fifty 

 miles south of the last mentioned locality ; and then only in summer. Ex- 

 tends from the Rio Grande valley to the Pacific. Numerous specimens are 

 in the Smithsonian from Cape St. Lucas. 



A female procured at Date Creek, June 5, 1865, differs from C. Henryi as 

 follows : The wing from the carpus measures 7 inches instead of about 8 ; 

 the tail 4^ instead of 5. The throat, though the specimen is a female, is pure 

 white ; but there are no white bands on the tail, the lateral rectrices having 

 very irregular, interrupted bands of rufous, except the middle pair, which are 

 barred with black and mottled gray, the latter much the widest. The pri- 

 maries are all basally spotted thickly on both inner and outer webs with bright 

 rufous, which spots show a tendency to form incomplete bars. On the three 

 first primaries is a large spot of very light rufous, placed within 2% inches of 



[March, 



