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July, 1908 ANNOTATED LIST OF THE BIRDS OF MESA COUNTY, COLORADO 165 the most common birds found in the County. Found at all altitudes during the summer and breeding abundantly wherever found. Its choice of a nesting place is varied. I have found it in cottonwoods, cedars, scrub-oak, pine and aspen. Winters along the streams in the lower part of the County, but not so plentiful in winter as in summer. Its breeding habits are rather uncertain; fresh eggs may be found during all of May and June. Phalaen0ptilus nuttalli. Poorwill. Summer resident, presumably common. Owing to its retiring habits and nocturnal proclivities I have very little information regarding this peculiar bird. One was collected for identification July 5, 1899, at about 6500 feet in the Plateau Valley, and I have seen several others up to 8000 feet, but have not found it nesting, altho it undoubtedly does breed in the County. Chordeiles virginianus henryi. Western Nighthawk. Summer resident, com- mon. A bird of the lower altitudes, much more common below 6500 feet than above, in fact it is rarely met with above 8000. Arrives rather late in the spring, seldom occurring in any abundance before May 1. Nests late in June, selecting dry rocky ridges or sage brush fiats as a nesting site. Departs for the south with the first frosts. Mr. Sulllvan's extreme dates of arrival and departure are May 8 and October 18. He says they are most abundant during the middle of August gradually diminishing after that date. [Cypseloicles niger borealis. Black Swift. Occurs regularly in Southxvestern Colorado and probably wanders into Mesa County from the south.] Aeronautes melanoleucus. White-throated Swift. Summer resident, of un- certain occurrence. The writer has occasionally seen large flocks of these birds, flying at a great height, pass over the Plateau Valley during the summer months, but their occurrence is very uncertain, and I do not think they breed in the eastern part of the County. My earliest arrival date is April 27, 1902. Mr. Sullivan says a large colony breeds in the "ragged faces of the cliffs near the Book Cliffs Coal Mine". Prof. Cooke states that they nest commonly at Whitewater. Trochilus platycercus. Broad-tailed Hummingbird. Summer resident, abun- dant. The only hummer I have found in the County, altho 7`. alexandrite' and ?'. rtt_/?s undoubtedly occur with greater or less regularity. Arrives early in May (May 4, 1902, is my earliest arrival date), and breeds during June and July. Frequents the timber along the streams from 6000 feet up and raises two broods in a season and possibly three. I found them breeding abundantly on Buzzard Creek at about 8000 and found nests containing fresh eggs, freshly hatched young and fledglings just ready to leave the nest on the same day and within a radius of half a mile. The nests are placed in pines, cottonwoods, and alders from 6 to 30 feet from the ground and almost invariably near or over running water. One nest found was built on a root protruding from a bank directly over and within 2 feet of the swift running water of Buzzard Cre?k. I have noted it as late as October 15 but I think the bulk migrate in September. Selasphorus rufus. Rufous Hummingbird. Quoting Miss Eggleston, "Irreg- ular migrant. This hummer is not often seen, but occasionally will be met with for a few days when the early flowers are out." ['l'yrannus tyranuus. Kingbird. It is hard to understand why this well khown bird has not been reported by some of the observers who have furnished the basis of this list, but tho special inquiry about this species has been made the writer has been unable to find any record of its occurrence in the County. It breeds in Middle Park, is known to occur rarely in Routt County and probably occurs occasionally in the Grand Valley.] Tyrannus verticalis. Arkansas Kingbird. Summer resident. I am not posi- tive as to the relative abundance of this species and 7'. voci?t)rans. Prof. Cooke in his 13trds of Colorado says of verlicah's, "Scarcely found in the mountains, rising