K Dixon 1950 Sialia mexicana. 1. Mar. 19. 'Artists' Camp', 1600 ft. Mt. Diablo, Contra Costa Co., Calif. For details of antagonism shown a pair of Plain Towhee over a nesting cavity, see species acct of the latter. Both ♂ + ♀ bluebird were involved at different times in attempts to drive the Towhee away. Apparently the open-ness of the woodland (here largely live oak) and proximity of grassland made this site attractive to the bluebirds. Apparently the Towhees were slightly more advanced in their nesting cycle for the ♀ carried materials, while the bluebirds were interested in selection + defense of a site but perhaps not ready to build. I did not see either bluebird enter the cavity; probably it was large enough to accomodate the bluebird. See species acct, Paurus. Apr. 15. Seilomar, Monterey Peninsula, Monterey Co., Calif. 8:00 AM Pair of Bluebirds seen perched in dead upper trunk of cypress tree. Nest-cavities apparently occupied by Violet-green Swallows - no sign of contest over cavities in one or two minutes of watching.