228 UNIVERSITY OF COLORADO STUDIES 



The question of secondary migration, with a second nesting at a 

 higher altitude, is also an interesting one. F. M. Drew 1 stated that 

 in San Juan County the White-crowned Sparrow raised its first brood 

 at a comparatively low elevation and then moved up to timberline for 

 a second nesting. A. W. Anthony, 2 in regard to the same question, 

 wrote as follows: 



These notes [Drew's] were verified by my own observations at Silverton in 

 1883, when White-crowns were found in abundance along the willow-lined streams 

 in May and June and several nests were taken. After the first week in July, 

 however, they were rather scarce in the lower valleys but suddenly made their 

 appearance about the snow banks above timberline where a second brood was 

 raised and where they remained in abundance until late in the fall. 



In this instance a migration certainly took place in the midst of the nesting 

 season. To what extent in latitude it is impossible to ascertain, but vertically 

 it could not have been less than 2,000 feet, and it is not unreasonable to suppose 

 that in gaining this elevation some distance was also gained in latitude. 



There appears to be no evidence as yet from Boulder County that 

 a similar migration takes place. Denis Gale found the White-crowns' 

 nests mostly from about 10,000 feet to timberline and between June 

 1 5 and July 20. He believed they nested but once. The presence of 

 migrants on the plains from the last of April to the first week in June 

 indicates that the individuals nesting at the highest altitudes may 

 be simply the late migrants. The writer has found White-crowned 

 Sparrows to be common at Tolland (9,000 feet) in the last of May 

 and in the middle of July, and also common at timberline in the 

 first week of July. 



In this connection Denis Gale wrote as follows concerning the 

 second nesting of the Robin : 



Judging from the greater number of nests of this second family raising, which 

 is early in July, I opine some of the birds have their first nests in the valley or 

 foothills, and choose the higher mountain canyons for their second. They are 

 not uncommon at timberline, 11,000 feet above sea-level, and at this point, in 

 many situations in which they are seen, young could not be raised until July. 



■ Bull. Nut. Orn. Club, Vol. VI, 1881. 



■ Zoe, Vol. I, p. 379, 1801. 



