180 



THE CONDOR 



Vol. X 



Planesticus migratorius propinquus. Western Robin. Summer resident, abun- 

 dant. One of the first arrivals in the spring, often being seen as early as February 

 15, and one of the commonest breeders from the lowest parts of the County up to 

 10,500 feet. My earliest date of arrival is February 8, and by March 15 they are 

 common. Nests wherever there is timber, during May and June, and raises two 

 broods. Performs a slight vertical migration as soon as the young are able to fly 

 and bands together in flocks for the fall migration in October and November. Mr. 

 Sullivan says, "Undoubtedly remain all winter; that is, a few here and there." 



[Sialia 'mexicana baitdi. Chestnut-backed Bhiebird. A western species that occurs 

 sparingly thruoait western Colorado. Probably occurs in Mesa County rather rarely in sunnner.] 





WESTERN ROBIN IN NEST BUILT UNDER STRAW ROOF OF ROUGH POLE 

 CATTLE SHED; MESA COUNTY 



Sialia arctica. Mountain Bluebird. Summer resident, abundant. Thruout 

 the dry cedar and sage-brush country the Mountain Bluebird is very abundant, 

 nesting in natural cavities in the cedars. Mr. Sullivan says they are not at all 

 common around Grand Junction after the spring migration is over. They are very 

 early migrants, arriving about the middle of February and nesting late in April 

 and in May and raising two broods. The bulk nest between 5000 and 6000 feet, 

 but they are not uncommon up to at least 7000. In the cultivated sections they 

 resort to gate-frames, bird boxes, etc., for nesting sites. The fall migration occurs 

 in October. Mr. Sullivan's extreme dates of arrival and departure are February 

 11 and October 16. 



Denver, Colorado, 



