April 1904] BIRDS OF THE HUACHUCA MOUNTAINS, ARIZONA. 63 



of March, when their numbers were suddenly greatly increased. At 

 this time they could be seen feeding in trees along the streams in flocks 

 of from fifteen to twenty-five individuals, being larger gatherings of 

 these birds than I have seen elsewhere. Though occurring in all parts 

 of the mountains up to the highest peaks, they were most abundant in 

 the canyons below 7000 feet ; and remained until about the middle of 

 May, the last being seen May 13th. In the fall, up to the time I left, 

 September 5th, they had not yet returned. 



Polioptila caerulea obscura Ridgway. Western Gnatcatcher. 



This is the only species of gnatcatcher I have observed in the 

 Huachucas. On the brush covered plains below, and along the San 

 Pedro River, pJiiiuhca breeds in moderate abundance, but 1 have never 

 seen it in the mountains, the ahitude being i^robably too high. Ob- 

 scura is probably resident in the Huachucas, though I have not found 

 it very abundant at any time : and it does not seem to range above 6500 

 feet, and but rarely to that altitude. It seemed more particularly to fre- 

 quent the rather barren foothill country, staying in the oaks and brush 

 high up on the hill sides rather than in the canyons. I saw several al- 

 ready paired on April 7th. 



Myadestes townsendi (Audulion). Townsend Solitaire. 



The Townsend Solitaire occurs in this region only as a migrant, 

 passing through early in the spring. The first noted was on March 7th, 

 and the last on April 30th. They were found in all parts of the range, 

 for I took specimens at nearly 10.000 feet, and others in the washes be- 

 low the mountains. They preferred rather open ground, and in the can- 

 yon I did most of my collecting in there was a large patch of cleared 

 ground which they seemed particularly to favor, and occasionally as 

 many as eight or ten birds could be seen sitting on the tops of the trees 

 surrounding the clearing. As a rule they stayed high up in the trees, 

 and were at all times shy and hard to approach. They were in full song 

 before they left. 



Hylocichla ustulata (Nuttall). Russet-backed Thrush. 

 Hylocichla ustulata swainsoni (Cabanis). Olive-backed Thrush. 



In i8g6 two thrushes from the Huachuca Mountains sent to Mr. 

 Ridgway to be identified were returned to him labelled, the one ustu- 

 lata, the other swainsoni. These two represent the extremes of color of 

 a considerable series of these birds from the region imder consideration, 

 the one (ustulata) being an extremely pale colored bird, sparselv marked 

 on the breast, indistinguishable from breeding birds from Southern Cal- 

 ifornia ; while the other (swainsoni) is a very dark colored lieavily 

 marked bird. Between these extremes the specimens collected form an 

 imbroken chain, so that it is impossible to say where the one ends and 

 the other begins, The series of szvainsoni are all very olivaceous in their 

 coloration, without any trace of the grayish on the upper parts that Mr. 

 Oberholzer ascribes to the sub-species ahnac. (Auk. XV, page 303), oth- 

 erwise I should think it more probable that the Huachuca Mountain 

 birds belonged to that race than to szi'ainso)ii. 



These two varieties appear in the spring at about the same time, 

 and in the same localities, being abundant along the streams in the 

 lower canyons at a time when most of the migrants have already passed 

 on to their breeding grounds. I have specimens of both ustulata am! 



