YDixon 1949 Parus inornatus Aug. 2 Berkeley, Alameda Co., Calif. This incident took place at Childs' residence at 741 Boynton Ave. Berkeley. Sept 26. Clear morning, 11:00 AM. I watched two Plain Titmice for 4 or 5 minutes as they moved through two walnut-like dead-wood trees at corner of Bancroft & College. My attention was called to the birds by repeated 'sip' notes such as are given for 'contact' purpose (apparently) by members of a pair. I noted both birds in the uppermost leafy branches of one tree, both individuals vibrating their wings but uttering no sounds at any time except for occasional 'contact' notes. I am not certain whether these were given by one or both birds. Suddenly a pursuit occurred following which both birds took perch several feet apart, lower in tree. I had an impression that the pursued individual vibrated its wings more noticeably. A second pursuit consisted of a short flight outward from the foliage with return to nearby leafy branches. Soon a third flight led to the tree adjacent to the south (on NE corner of intersection, I watched from SW corner). There was further shifting of perches in this tree and I had one view (of the pursuer?) perch'd near periphery of tree. My departure on a bus halted observations. Whether this represented territorial defense or possible preliminary pairing behavior, I am unable to say from limited observation. (written during evening, Sept 26).