Posted by Gary Potter (152.163.201.46) on March 02, 2000 at 22:16:18:
I think the thrasher is a Curve-billed. The mandible is only slightly curved, but I think that it is within the range of both Curve-billed and Bendire's. A more important point is that the base of the mandible does not appear to be pale, although there is a lighter highlight in this area, it is also present on the maxilla just below the nostril. A Bendire's should have a considerably more conspicuous light buffy area on the mandible, with no corresponding light area on the maxilla. Also the bill seems to be black, not dark gray, which also indicates Curve-billed. The yellowish eye is within the range of both species, and the breast spotting could be either species also. The background color of the breast is more brownish than whitish which is more typical of Bendire's, but at least some of the spots seem to be quite large and roundish, which is more typical of Curve-billed.
My first impression was that the Bluebird is a female Mountain. After more study I find nothing to disuade me from my original impression. The shade of blue looks like a typical Mountain as do the light underparts with only a slight hint of rusty brown which seems to eliminate Western Bluebird (and Eastern as well!). The primary extension looks longish, but the angle & exposure of the photograph may be misleading in this respect.