284 BULLETIN 19 6, UNITED STATES NATIONAL MUSEUM 



late in September and early in October of 1929, in Colorado, I heard 

 the song of this species. It was a beautiful, clear, short warble, 

 higher-pitched than that of S. sialis and hardly suggesting it. The 

 call notes were sweet and soft, very much like those of the eastern 

 bluebird, but not so clear or so loud." 



Claude T. Barnes writes to me from Utah: "Sitting on a clothes- 

 line, a female bluebird resented my approach by a click, several times 

 repeated; then at last it sang its very soft, charming song: Trill, trill, 

 trill, a mellow roll uttered without opening its bill. The number of 

 trlls varied from one to half a dozen, but I am positive the bird 

 never once opened its bill during the ten minutes that I watched it 

 without taking the glasses from my eyes. This habit is, no doubt, 

 somewhat responsible for the subdued nature of the lovely bird's 

 song." 



Mrs. Wheelock (1904) refers to the song as "a sweet clear 'trually, 

 tru-al-ly,' like that of the Eastern species, and a mellow warble." 

 And Winton Weydemeyer (1934a) writes: 



On frequent occasions during the last seven summers I have forsaken the com- 

 fort of my bed to enjoy their subdued, gentle singing. For one must be an early 

 riser indeed if he wishes to hear the Mountain Bluebird's song. Singing com- 

 mences in full darkness, and continues for a few minutes to as much as an hour, 

 ceasing soon after daylight. * * * Only once during the past seven years 

 have I heard the bird's song at any other time of the day: At 9 o'clock on a dark, 

 rainy morning in March of 1932, a Mountain Bluebird gave weakly a few snatches 

 of its usual daybreak song. 



In form, the song is almost a replica of the familiar caroling of the Western 

 Robin; but it is given very softly, crooningly, with an unmistakable quality of 

 the Bluebird's gentle call. Though I have not determined the distance at which 

 the singing can be heard, I doubt if it is audible at seventy yards. The notes are 

 repeated over and over, without a pause, for as much as thirty minutes at a time. 



Because of the marked resemblance to the song of the Robin, * * * the 

 song of the Mountain Bluebird appears to be a possible illustration of retrogres- 

 sion in the evolution of bird song. It seems probable that the song, at some time 

 in the past, was louder and more varied, and was sung more commonly, than it 

 is now; and that it is gradually being lost, even as the species is losing other 

 thrush-like characters. If this be so, it is possible that some or all of the Moun- 

 tain Bluebirds in some parts of their breeding range are already songless, as the 

 testimony of many writers indicates. 



Field marks.— The male mountain bluebird is unmistakable in his 

 beautiful coat of plain cerulean or turquoise blue, with only a shading 

 of dusky in his wing tips. The female is modestly clad in a pale 

 brownish or buff gray, with a tinge of bluish on the upper surface. 

 Both can be distinguished from the western bluebird by the entire 

 absence of chestnut. The blue is much paler than in most other blue 

 birds, except the lazuli bunting, which is a smaller bud and has white 

 wing bars. 



Enemies. — Other hole-nesting birds are competitors for nesting 



