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TIlE CONDOR VOL. X Planesticus migrat0rius propinquusJ 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 bairdi. Chestnut-backed Bluebird. A western species that occurs sparingly thruout western Colorado. Probably occurs in Mesa County rather rarely in summer.] WI?.;STIq.;RN ROllIN IN Iqlq.;ST BUILT UNDER STRAW ROOF OF ROUGH CATT[,I*.; SHED: MF..qA 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, et.c., for nesting sites. The fall migration occurs in October. Mr. Sullivan's extreme dates of arrival and departure are February 11 and October 16. 2)enver, Colorado.