3^2 Henshaw on Birds observed in Netv Mexico. [October 



north in considerable numbers about August 25. By September 20 it be- 

 gan to be uncommon. The last individual was seen September 28. It 

 was always found associated with flocks of various other birds, and 

 chiefly frequented the pines. The disproportionate number of young 

 birds over old ones was very noticeable, not more than half a dozen 

 of the latter being seen. 



It would be interesting to know from just what source these Rocky 

 Mountain migrants are derived, and why if, as seems probable, they come 

 from the Sierras, they select this route instead of taking a due southern 

 course. The species is unknown in the Rocky Mountains in spring, ex- 

 cept along the southern border. 



17. Geothlypis macgillivrayi. Macgillivray's Warbler. — This is 

 another species which, as a summer resident, was to be expected. Not 

 one was seen, however, until the bird appeared from the north, which it 

 did the last days of August. In early September it became fairly common 

 in the thickets along the streams. 



18. Myiodioctes pusillus. Wilson's Blackcap. — So far as we could 

 ascertain, this bird did not breed in the locality. The first one was seen 

 August 8. It soon became extremely numerous; nowhere, in fact, have I 

 ever seen it so abundant. It was found in every flock of migrants, and also 

 in companies of half a dozen or more among the alders and willows of the 

 streams. 



19. Vireo gilvus swainsoni. Swainson's Vireo. — Fairly numerous 

 as a summer resident, though by no means so common as it is farther 

 north. This locality may be, in fact, near the extremity of its southern 

 limit in summer. 



20. Vireo solitarius plumbeus. Plumbeus Vireo. — Rather common 

 in summer, but not nearly so numerous as the bird is at this season in 

 Colorado and other points to the northward. Almost exclusively restricted 

 to the pines. 



21. Vireo solitarius cassini. Cassin's Vireo. — This is another Pacific 

 coast form, many individuals of which, for some unexplained reason, 

 choose to reach their southern winter quarters by way of the Rocky Moun~ 

 tains rather than to follow the Sierras, where alone it is known to breed. 

 It also is not known to occur in the Rocky Mountains in spring, except in 

 the extreme southern portion of the range. It was first seen September 2 

 and soon became fairly numerous. It was found in the pines moving 

 about with the Warblers and other migrating birds, but it also frequented 

 the aspens and oak brush. It was a noticeable fact that while this bird 

 was quite silent, the Plumbeous Vireo, which was now moulting its worn 

 summer plumage, prior to moving south, was frequently in song, being, 

 in fact, the only species that was so. 



22. Lanius ludovicianus excubitoroides. White-rumped Shrike. — 

 A single bird was shot among some dead timber well up on a mountain 

 ridge. The bird seemed to be quite out of place among its surroundings, 

 and was, I presume, nothing but a straggler from the lower regions east- 

 ward. 



