MiNOT on Colorado Birds. 231 



liquid. It is sonietimes prolonged to an attempted -warble. Tlieir other 

 notes are a liquid chuck and a whistled pheu (wonderfully like a Thrush's, 

 yet akin to the Red-wing's), a chatter, and quite a liquid trill : also a 

 petulant note (?). 



38. Contopus borealis, Brtw/. Olive-sided Flycatcher. — This 

 bird I found rare at Boulder in May, but common on Pike's Peak in June, 

 in and about spruce timber, above 10,000 feet. T often heard their loud 

 whistled wh'che-be'-u. Their ordinary chup-chup-chup-chvp, or bil-bil, is 

 Finch-like ; while, when they are excited, the rapid succession of their 

 whistled notes might readily pass for a song. (Occasionally with a pecu- 

 liar loud, harsh, almost abrupt pu-ee f) 



39. Contopus virens richardsoni, Baird. Western Wood Pewee. 

 — At Boulder, rather common after May 25. Song-notes, a harsh pe-ee 

 or pee-tcee, with nothing of the plaintive drawl of the Eastern bird (and 

 perhaps, occasionally, a ch'pe'-bu or cVpe'-phii). These birds I often found 

 with the following. 



40. Empidonax trailli pusillus, Couest. Western Traill's Fly- 

 catcher. — Common in shrubbery on or near the plains, and not at all 

 shy. I found them already at Boulder, May 15. They habitually flirt 

 the tail. Ordinary notes : whit and pu-ee' (and perhaps song-notes of 

 ch'phe-hee'^. 



41. Empidonax hammondi, Baird. Hammond's Flycatcher. — • 

 Similar io pusillus \n habits and coloring, but with colors more contrasted. 

 Ordinary note, an almost whistled pip or phip; song-note, tch'che'-be'-u or 

 wkit-ck'bec' , not very abrupt, but with the head tossed. I nowhere found 

 this species common. 



42. Empidonax flaviventris difiScilis, Allen. Western Yellow 

 bellied Flycatcher. — A common summer resident up to 8,000 feet. 

 Notes, a chip, a single clear whistle, pee, and then pce-?<;ee, tolerably shrill, 

 and in no way loud, plaintive, or drawling, but slender, clear, and rather 

 decisive. Tail not flirted. This bird sometimes prefers a high, bare 

 perch. Mr. Aiken speaks of its singing. I heard once a ch'pee'-wee-pee'- 

 wee-pec' that I attributed to this species. May 21, 8,500 feet up, I observed 

 a pair of Flycatchers that puzzled me : they were active, pertinacious, noisy 

 little fellows, persistently remaining near the tops of spruces, especially 

 dead ones, and taking their flights, often vigorously, at that elevation ; 

 their notes were quick and generally shrill : ch'pulty-wa'ke, ch'pith/-wa'ke, 

 cWpe-wee', ch'pu-ee', etc., besides shrill twitters, guttural sounds, and 

 almost chattering. Could these have been the Yellow-bellied Flycatch- 

 ers in the mating season ? I failed to identify. 



43. Panyptila saxatilis, Cones. White-throated Swift. — Rare 

 about Boulder. About Manitou I found several communities and other 

 pairs occupying canons and cliffs, but often visiting the village. Their 

 sharp, vehement, rather coarse notes suggest at times a Woodpecker. 

 Their nests, as well as I can make out, are of glued twigs, either resting in 



